Pytest Documentation: Release 2.7.1

pytest Documentation
Release 2.7.1
holger krekel, trainer and consultant, http://merlinux.eu
May 19, 2015

CONTENTS
1 Getting started basics 3

1.1 pytest: helps you write better programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Installation and Getting Started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Usage and Invocations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4 Good Integration Practises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.5 Project examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.6 Some Issues and Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2 pytest reference documentation 21

2.1 Pytest API and builtin fixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.2 Basic test configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.3 The writing and reporting of assertions in tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.4 pytest fixtures: explicit, modular, scalable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.5 Fixture functions using “yield” / context manager integration . . . . . . . . . . . . . . . . . . . . . . 46
2.6 Parametrizing fixtures and test functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
2.7 classic xunit-style setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
2.8 Capturing of the stdout/stderr output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
2.9 Monkeypatching/mocking modules and environments . . . . . . . . . . . . . . . . . . . . . . . . . 54
2.10 xdist: pytest distributed testing plugin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
2.11 Temporary directories and files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
2.12 Marking test functions with attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
2.13 Skip and xfail: dealing with tests that can not succeed . . . . . . . . . . . . . . . . . . . . . . . . . 61
2.14 Asserting deprecation and other warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
2.15 Support for unittest.TestCase / Integration of fixtures . . . . . . . . . . . . . . . . . . . . . . . . . . 66
2.16 Running tests written for nose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
2.17 Doctest integration for modules and test files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
3 Working with plugins and conftest files 73

3.1 conftest.py: local per-directory plugins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
3.2 Installing External Plugins / Searching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
3.3 Writing a plugin by looking at examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
3.4 Making your plugin installable by others . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
3.5 Plugin discovery order at tool startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
3.6 Requiring/Loading plugins in a test module or conftest file . . . . . . . . . . . . . . . . . . . . . . . 75
3.7 Accessing another plugin by name . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
3.8 Finding out which plugins are active . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
3.9 Deactivating / unregistering a plugin by name . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
4 pytest default plugin reference 77
5 pytest hook reference 79
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5.1 Hook specification and validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.2 Initialization, command line and configuration hooks . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.3 Generic “runtest” hooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
5.4 Collection hooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
5.5 Reporting hooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.6 Debugging/Interaction hooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.7 Declaring new hooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.8 Using hooks from 3rd party plugins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
5.9 hookwrapper: executing around other hooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
6 Reference of objects involved in hooks 85
7 List of Third-Party Plugins 89
8 Usages and Examples 93

8.1 Demo of Python failure reports with pytest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
8.2 Basic patterns and examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
8.3 Parametrizing tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
8.4 Working with custom markers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
8.5 A session-fixture which can look at all collected tests . . . . . . . . . . . . . . . . . . . . . . . . . . 131
8.6 Changing standard (Python) test discovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
8.7 Working with non-python tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
9 Talks and Tutorials 139

9.1 Talks and blog postings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
9.2 Older conference talks and tutorials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
10 Contribution getting started 141

10.1 Submit a plugin, co-develop pytest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
10.2 Report bugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
10.3 Submit feedback for developers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
10.4 Fix bugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
10.5 Implement features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
10.6 Write documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
10.7 Preparing Pull Requests on Bitbucket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
10.8 Using git with bitbucket/hg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
11 pytest-2.3: reasoning for fixture/funcarg evolution 145

11.1 Shortcomings of the previous pytest_funcarg__ mechanism . . . . . . . . . . . . . . . . . . . 145
11.2 Direct scoping of fixture/funcarg factories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
11.3 Direct parametrization of funcarg resource factories . . . . . . . . . . . . . . . . . . . . . . . . . . 146
11.4 No pytest_funcarg__ prefix when using @fixture decorator . . . . . . . . . . . . . . . . . . . 146
11.5 solving per-session setup / autouse fixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
11.6 funcargs/fixture discovery now happens at collection time . . . . . . . . . . . . . . . . . . . . . . . 147
11.7 Conclusion and compatibility notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
12 Release announcements 149

12.1 pytest-2.7.1: bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
12.2 pytest-2.7.0: fixes, features, speed improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
12.3 pytest-2.6.3: fixes and little improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
12.4 Changes 2.6.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
12.5 pytest-2.6.2: few fixes and cx_freeze support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
12.6 pytest-2.6.1: fixes and new xfail feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
12.7 Changes 2.6.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
12.8 pytest-2.6.0: shorter tracebacks, new warning system, test runner compat . . . . . . . . . . . . . . . 153
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12.9 pytest-2.5.2: fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
12.10 pytest-2.5.1: fixes and new home page styling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
12.11 pytest-2.5.0: now down to ZERO reported bugs! . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
12.12 pytest-2.4.2: colorama on windows, plugin/tmpdir fixes . . . . . . . . . . . . . . . . . . . . . . . . 158
12.13 pytest-2.4.1: fixing three regressions compared to 2.3.5 . . . . . . . . . . . . . . . . . . . . . . . . . 159
12.14 pytest-2.4.0: new fixture features/hooks and bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . 159
12.15 pytest-2.3.5: bug fixes and little improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
12.16 pytest-2.3.4: stabilization, more flexible selection via “-k expr” . . . . . . . . . . . . . . . . . . . . 163
12.17 pytest-2.3.3: integration fixes, py24 suport, */** shown in traceback . . . . . . . . . . . . . . . . . 164
12.18 pytest-2.3.2: some fixes and more traceback-printing speed . . . . . . . . . . . . . . . . . . . . . . . 165
12.19 pytest-2.3.1: fix regression with factory functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
12.20 pytest-2.3: improved fixtures / better unittest integration . . . . . . . . . . . . . . . . . . . . . . . . 166
12.21 pytest-2.2.4: bug fixes, better junitxml/unittest/python3 compat . . . . . . . . . . . . . . . . . . . . 168
12.22 pytest-2.2.2: bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
12.23 pytest-2.2.1: bug fixes, perfect teardowns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
12.24 py.test 2.2.0: test marking++, parametrization++ and duration profiling . . . . . . . . . . . . . . . . 170
12.25 py.test 2.1.3: just some more fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
12.26 py.test 2.1.2: bug fixes and fixes for jython . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
12.27 py.test 2.1.1: assertion fixes and improved junitxml output . . . . . . . . . . . . . . . . . . . . . . . 173
12.28 py.test 2.1.0: perfected assertions and bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
12.29 py.test 2.0.3: bug fixes and speed ups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
12.30 py.test 2.0.2: bug fixes, improved xfail/skip expressions, speed ups . . . . . . . . . . . . . . . . . . . 175
12.31 py.test 2.0.1: bug fixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
12.32 py.test 2.0.0: asserts++, unittest++, reporting++, config++, docs++ . . . . . . . . . . . . . . . . . . 177
13 Changelog history 181

13.1 2.7.1 (compared to 2.7.0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
13.2 2.7.0 (compared to 2.6.4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
13.3 2.6.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
13.4 2.6.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
13.5 2.6.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
13.6 2.6.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
13.7 2.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
13.8 2.5.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
13.9 2.5.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
13.10 2.5.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
13.11 v2.4.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
13.12 v2.4.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
13.13 v2.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
13.14 v2.3.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
13.15 v2.3.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
13.16 v2.3.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
13.17 v2.3.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
13.18 v2.3.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
13.19 v2.3.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
13.20 v2.2.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
13.21 v2.2.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
13.22 v2.2.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
13.23 v2.2.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
13.24 v2.2.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
13.25 v2.1.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
13.26 v2.1.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
13.27 v2.1.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
13.28 v2.1.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
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13.29 v2.0.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
13.30 v2.0.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
13.31 v2.0.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
13.32 v2.0.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
13.33 v1.3.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
13.34 v1.3.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
13.35 v1.3.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
13.36 v1.3.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
13.37 v1.3.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
13.38 v1.2.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
13.39 v1.1.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
13.40 v1.1.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
13.41 v1.0.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
13.42 v1.0.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
13.43 v1.0.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
13.44 v1.0.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
13.45 v1.0.0b9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
13.46 v1.0.0b8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
13.47 v1.0.0b7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
13.48 v1.0.0b3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
13.49 v1.0.0b1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
13.50 v0.9.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
13.51 v0.9.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
Index 211
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pytest Documentation, Release 2.7.1
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CHAPTER
ONE
GETTING STARTED BASICS
1.1 pytest: helps you write better programs
a mature full-featured Python testing tool

• runs on Posix/Windows, Python 2.6-3.4, PyPy and (possibly still) Jython-2.5.1
• well tested with more than a thousand tests against itself
• strict backward compatibility policy for safe pytest upgrades
• comprehensive online and PDF documentation
• many third party plugins and builtin helpers,
• used in many small and large projects and organisations
• comes with many tested examples
provides easy no-boilerplate testing
• makes it easy to get started, has many usage options
• Asserting with the assert statement
• helpful traceback and failing assertion reporting
• print debugging and the capturing of standard output during test execution
scales from simple unit to complex functional testing
• modular parametrizeable fixtures (new in 2.3, continuously improved)
• parametrized test functions
• Marking test functions with attributes
• Skip and xfail: dealing with tests that can not succeed (improved in 2.4)
• distribute tests to multiple CPUs through xdist plugin
• continuously re-run failing tests
• flexible Conventions for Python test discovery
integrates with other testing methods and tools:
• multi-paradigm: pytest can run nose, unittest and doctest style test suites, including running testcases
made for Django and trial
• supports good integration practises
• supports extended xUnit style setup
3
• supports domain-specific Working with non-python tests

• supports generating test coverage reports
• supports PEP 8 compliant coding styles in tests
extensive plugin and customization system:
• all collection, reporting, running aspects are delegated to hook functions
• customizations can be per-directory, per-project or per PyPI released plugin
• it is easy to add command line options or customize existing behaviour
1.2 Installation and Getting Started
Pythons: Python 2.6,2.7,3.3,3.4, Jython, PyPy-2.3

Platforms: Unix/Posix and Windows
PyPI package name: pytest
dependencies: py, colorama (Windows), argparse (py26).
documentation as PDF: download latest
1.2.1 Installation
Installation options:
pip install -U pytest # or
easy_install -U pytest
To check your installation has installed the correct version:

$ py.test --version
This is pytest version 2.7.1, imported from /tmp/sandbox/pytest/.tox/regen/lib/python3.4/site-package
If you get an error checkout Known Installation issues.
1.2.2 Our first test run
Let’s create a first test file with a simple test function:

# content of test_sample.py
def func(x):
return x + 1
def test_answer():
assert func(3) == 5
That’s it. You can execute the test function now:

$ py.test
=========================== test session starts ============================
platform linux -- Python 3.4.1 -- py-1.4.27 -- pytest-2.7.1
rootdir: /tmp/doc-exec-101, inifile:
collected 1 items
4 Chapter 1. Getting started basics

test_sample.py F
================================= FAILURES =================================

_______________________________ test_answer ________________________________
def test_answer():
> assert func(3) == 5
E assert 4 == 5
E + where 4 = func(3)
test_sample.py:5: AssertionError
========================= 1 failed in 0.01 seconds =========================
pytest found the test_answer function by following standard test discovery rules, basically detecting the
test_ prefixes. We got a failure report because our little func(3) call did not return 5.
Note: You can simply use the assert statement for asserting test expectations. pytest’s Advanced assertion intro-
spection will intelligently report intermediate values of the assert expression freeing you from the need to learn the
many names of JUnit legacy methods.
1.2.3 Asserting that a certain exception is raised
If you want to assert that some code raises an exception you can use the raises helper:
# content of test_sysexit.py
import pytest
def f():
raise SystemExit(1)
def test_mytest():
with pytest.raises(SystemExit):
f()
Running it with, this time in “quiet” reporting mode:

$ py.test -q test_sysexit.py
.
1 passed in 0.01 seconds
Todo
For further ways to assert exceptions see the raises
1.2.4 Grouping multiple tests in a class
Once you start to have more than a few tests it often makes sense to group tests logically, in classes and modules. Let’s
write a class containing two tests:
# content of test_class.py
class TestClass:
def test_one(self):
x = "this"
assert 'h' in x
1.2. Installation and Getting Started 5

def test_two(self):
x = "hello"
assert hasattr(x, 'check')
The two tests are found because of the standard Conventions for Python test discovery. There is no need to subclass
anything. We can simply run the module by passing its filename:
$ py.test -q test_class.py
.F
================================= FAILURES =================================
____________________________ TestClass.test_two ____________________________
self = <test_class.TestClass object at 0x7fbf54cf5668>
def test_two(self):
x = "hello"
> assert hasattr(x, 'check')
E assert hasattr('hello', 'check')
test_class.py:8: AssertionError
1 failed, 1 passed in 0.01 seconds
The first test passed, the second failed. Again we can easily see the intermediate values used in the assertion, helping
us to understand the reason for the failure.
1.2.5 Going functional: requesting a unique temporary directory
For functional tests one often needs to create some files and pass them to application objects. pytest provides Builtin
fixtures/function arguments which allow to request arbitrary resources, for example a unique temporary directory:
# content of test_tmpdir.py
def test_needsfiles(tmpdir):
print (tmpdir)
assert 0
We list the name tmpdir in the test function signature and pytest will lookup and call a fixture factory to create
the resource before performing the test function call. Let’s just run it:
$ py.test -q test_tmpdir.py
F
================================= FAILURES =================================
_____________________________ test_needsfiles ______________________________
tmpdir = local('/tmp/pytest-18/test_needsfiles0')
def test_needsfiles(tmpdir):
print (tmpdir)
> assert 0
E assert 0
test_tmpdir.py:3: AssertionError
--------------------------- Captured stdout call ---------------------------
/tmp/pytest-18/test_needsfiles0
1 failed in 0.05 seconds
Before the test runs, a unique-per-test-invocation temporary directory was created. More info at Temporary directories
and files.

You can find out what kind of builtin pytest fixtures: explicit, modular, scalable exist by typing:
py.test --fixtures # shows builtin and custom fixtures
1.2.6 Where to go next
Here are a few suggestions where to go next:

• Calling pytest through python -m pytest for command line invocation examples
• good practises for virtualenv, test layout, genscript support
• pytest fixtures: explicit, modular, scalable for providing a functional baseline to your tests
• pytest reference documentation for documentation and examples on using pytest
• Working with plugins and conftest files managing and writing plugins
1.2.7 Known Installation issues
easy_install or pip not found?
Install pip for a state of the art python package installer.

Install setuptools to get easy_install which allows to install .egg binary format packages in addition to source-
based ones.
py.test not found on Windows despite installation?
• Windows: If “easy_install” or “py.test” are not found you need to add the Python script path to your PATH,
see here: Python for Windows. You may alternatively use an ActivePython install which does this for you
automatically.
• Jython2.5.1 on Windows XP: Jython does not create command line launchers so py.test will not work
correctly. You may install py.test on CPython and type py.test --genscript=mytest and then use
jython mytest to run your tests with Jython using pytest.
Usages and Examples for more complex examples
1.3 Usage and Invocations
1.3.1 Calling pytest through python -m pytest
New in version 2.0.

If you use Python-2.5 or later you can invoke testing through the Python interpreter from the command line:
python -m pytest [...]
This is equivalent to invoking the command line script py.test [...] directly.
1.3. Usage and Invocations 7

1.3.2 Getting help on version, option names, environment variables
py.test --version # shows where pytest was imported from

py.test --fixtures # show available builtin function arguments
py.test -h | --help # show help on command line and config file options
1.3.3 Stopping after the first (or N) failures
To stop the testing process after the first (N) failures:

py.test -x # stop after first failure
py.test --maxfail=2 # stop after two failures
1.3.4 Specifying tests / selecting tests
Several test run options:

py.test test_mod.py # run tests in module
py.test somepath # run all tests below somepath
py.test -k stringexpr # only run tests with names that match the
# the "string expression", e.g. "MyClass and not method"
# will select TestMyClass.test_something
# but not TestMyClass.test_method_simple
py.test test_mod.py::test_func # only run tests that match the "node ID",
# e.g "test_mod.py::test_func" will select
# only test_func in test_mod.py
Import ‘pkg’ and use its filesystem location to find and run tests:
py.test --pyargs pkg # run all tests found below directory of pypkg
1.3.5 Modifying Python traceback printing
Examples for modifying traceback printing:

py.test --showlocals # show local variables in tracebacks
py.test -l # show local variables (shortcut)
py.test --tb=long # the default informative traceback formatting

py.test --tb=native # the Python standard library formatting
py.test --tb=short # a shorter traceback format
py.test --tb=line # only one line per failure
1.3.6 Dropping to PDB (Python Debugger) on failures
Python comes with a builtin Python debugger called PDB. pytest allows one to drop into the PDB prompt via a
command line option:
py.test --pdb
This will invoke the Python debugger on every failure. Often you might only want to do this for the first failing test to
understand a certain failure situation:

py.test -x --pdb # drop to PDB on first failure, then end test session
py.test --pdb --maxfail=3 # drop to PDB for first three failures
Note that on any failure the exception information is stored on sys.last_value, sys.last_type and
sys.last_traceback. In interactive use, this allows one to drop into postmortem debugging with any debug
tool. One can also manually access the exception information, for example:
>> import sys
>> sys.last_traceback.tb_lineno
42
>> sys.last_value
AssertionError('assert result == "ok"',)
1.3.7 Setting a breakpoint / aka set_trace()
If you want to set a breakpoint and enter the pdb.set_trace() you can use a helper:
import pytest
def test_function():
...
pytest.set_trace() # invoke PDB debugger and tracing
Prior to pytest version 2.0.0 you could only enter PDB tracing if you disabled capturing on the command line via
py.test -s. In later versions, pytest automatically disables its output capture when you enter PDB tracing:
• Output capture in other tests is not affected.
• Any prior test output that has already been captured and will be processed as such.
• Any later output produced within the same test will not be captured and will instead get sent directly to
sys.stdout. Note that this holds true even for test output occuring after you exit the interactive PDB tracing
session and continue with the regular test run.
Since pytest version 2.4.0 you can also use the native Python import pdb;pdb.set_trace() call to enter PDB
tracing without having to use the pytest.set_trace() wrapper or explicitly disable pytest’s output capturing
via py.test -s.
1.3.8 Profiling test execution duration
To get a list of the slowest 10 test durations:

py.test --durations=10
1.3.9 Creating JUnitXML format files
To create result files which can be read by Hudson or other Continuous integration servers, use this invocation:
py.test --junitxml=path
to create an XML file at path.
1.3.10 Creating resultlog format files
To create plain-text machine-readable result files you can issue:
1.3. Usage and Invocations 9

py.test --resultlog=path
and look at the content at the path location. Such files are used e.g. by the PyPy-test web page to show test results
over several revisions.
1.3.11 Sending test report to online pastebin service
Creating a URL for each test failure:

py.test --pastebin=failed
This will submit test run information to a remote Paste service and provide a URL for each failure. You may select
tests as usual or add for example -x if you only want to send one particular failure.
Creating a URL for a whole test session log:
py.test --pastebin=all
Currently only pasting to the http://bpaste.net service is implemented.
1.3.12 Disabling plugins
To disable loading specific plugins at invocation time, use the -p option together with the prefix no:.
Example: to disable loading the plugin doctest, which is responsible for executing doctest tests from text files,
invoke py.test like this:
py.test -p no:doctest
1.3.13 Calling pytest from Python code
New in version 2.0.

You can invoke pytest from Python code directly:
pytest.main()
this acts as if you would call “py.test” from the command line. It will not raise SystemExit but return the exitcode
instead. You can pass in options and arguments:
pytest.main(['-x', 'mytestdir'])
or pass in a string:
pytest.main("-x mytestdir")
You can specify additional plugins to pytest.main:

# content of myinvoke.py
import pytest
class MyPlugin:
def pytest_sessionfinish(self):
print("*** test run reporting finishing")
pytest.main("-qq", plugins=[MyPlugin()])
Running it will show that MyPlugin was added and its hook was invoked:

$ python myinvoke.py
*** test run reporting finishing
1.4 Good Integration Practises
1.4.1 Work with virtual environments
We recommend to use virtualenv environments and use pip (or easy_install) for installing your application and any
dependencies as well as the pytest package itself. This way you will get an isolated and reproducible environment.
Given you have installed virtualenv and execute it from the command line, here is an example session for unix or
windows:
virtualenv . # create a virtualenv directory in the current directory
source bin/activate # on unix
scripts/activate # on Windows
We can now install pytest:

pip install pytest
Due to the activate step above the pip will come from the virtualenv directory and install any package into the
isolated virtual environment.
1.4.2 Choosing a test layout / import rules
pytest supports two common test layouts:

• putting tests into an extra directory outside your actual application code, useful if you have many functional
tests or for other reasons want to keep tests separate from actual application code (often a good idea):
setup.py # your distutils/setuptools Python package metadata
mypkg/
__init__.py
appmodule.py
tests/
test_app.py
...
• inlining test directories into your application package, useful if you have direct relation between (unit-)test and
application modules and want to distribute your tests along with your application:
setup.py # your distutils/setuptools Python package metadata
mypkg/
__init__.py
appmodule.py
...
test/
test_app.py
...
Important notes relating to both schemes:

• make sure that “mypkg” is importable, for example by typing once:
1.4. Good Integration Practises 11

pip install -e . # install package using setup.py in editable mode
• avoid “__init__.py” files in your test directories. This way your tests can run easily against an installed version
of mypkg, independently from the installed package if it contains the tests or not.
• With inlined tests you might put __init__.py into test directories and make them installable as part of
your application. Using the py.test --pyargs mypkg invocation pytest will discover where mypkg is
installed and collect tests from there. With the “external” test you can still distribute tests but they will not be
installed or become importable.
Typically you can run tests by pointing to test directories or modules:
py.test tests/test_app.py # for external test dirs
py.test mypkg/test/test_app.py # for inlined test dirs
py.test mypkg # run tests in all below test directories
py.test # run all tests below current dir
...
Because of the above editable install mode you can change your source code (both tests and the app) and
rerun tests at will. Once you are done with your work, you can use tox to make sure that the package is really correct
and tests pass in all required configurations.
Note: You can use Python3 namespace packages (PEP420) for your application but pytest will still perform test
package name discovery based on the presence of __init__.py files. If you use one of the two recommended file
system layouts above but leave away the __init__.py files from your directories it should just work on Python3.3
and above. From “inlined tests”, however, you will need to use absolute imports for getting at your application code.
Note: If pytest finds a “a/b/test_module.py” test file while recursing into the filesystem it determines the import
name as follows:
• determine basedir: this is the first “upward” (towards the root) directory not containing an __init__.py.
If e.g. both a and b contain an __init__.py file then the parent directory of a will become the basedir.
• perform sys.path.insert(0, basedir) to make the test module importable under the fully qualified
import name.
• import a.b.test_module where the path is determined by converting path separators / into ”.” charac-
ters. This means you must follow the convention of having directory and file names map directly to the import
names.
The reason for this somewhat evolved importing technique is that in larger projects multiple test modules might import
from each other and thus deriving a canonical import name helps to avoid surprises such as a test modules getting
imported twice.
1.4.3 Use tox and Continuous Integration servers
If you frequently release code and want to make sure that your actual package passes all tests you may want to look
into tox, the virtualenv test automation tool and its pytest support. Tox helps you to setup virtualenv environments with
pre-defined dependencies and then executing a pre-configured test command with options. It will run tests against the
installed package and not against your source code checkout, helping to detect packaging glitches.
If you want to use Jenkins you can use the --junitxml=PATH option to create a JUnitXML file that Jenkins can
pick up and generate reports.

1.4.4 Create a pytest standalone script
If you are a maintainer or application developer and want people who don’t deal with python much to easily run tests
you may generate a standalone pytest script:
py.test --genscript=runtests.py
This generates a runtests.py script which is a fully functional basic pytest script, running unchanged under
Python2 and Python3. You can tell people to download the script and then e.g. run it like this:
python runtests.py
1.4.5 Integrating with distutils / python setup.py test
You can integrate test runs into your distutils or setuptools based project. Use the genscript method to generate a
standalone pytest script:
py.test --genscript=runtests.py
and make this script part of your distribution and then add this to your setup.py file:
from distutils.core import setup, Command
# you can also import from setuptools
class PyTest(Command):
user_options = []
def initialize_options(self):
pass
def finalize_options(self):
pass
def run(self):
import subprocess
import sys
errno = subprocess.call([sys.executable, 'runtests.py'])
raise SystemExit(errno)
setup(
#...,
cmdclass = {'test': PyTest},
#...,
)
If you now type:

python setup.py test
this will execute your tests using runtests.py. As this is a standalone version of pytest no prior installation
whatsoever is required for calling the test command. You can also pass additional arguments to the subprocess-calls
such as your test directory or other options.
1.4.6 Integration with setuptools test commands
Setuptools supports writing our own Test command for invoking pytest. Most often it is better to use tox instead, but
here is how you can get started with setuptools integration:

import sys
from setuptools.command.test import test as TestCommand
class PyTest(TestCommand):
user_options = [('pytest-args=', 'a', "Arguments to pass to py.test")]
def initialize_options(self):
TestCommand.initialize_options(self)
self.pytest_args = []
def finalize_options(self):
TestCommand.finalize_options(self)
self.test_args = []
self.test_suite = True
def run_tests(self):
#import here, cause outside the eggs aren't loaded
import pytest
errno = pytest.main(self.pytest_args)
sys.exit(errno)
setup(
#...,
tests_require=['pytest'],
cmdclass = {'test': PyTest},
)
Now if you run:

python setup.py test
this will download pytest if needed and then run your tests as you would expect it to. You can pass a single string
of arguments using the --pytest-args or -a command-line option. For example:
python setup.py test -a "--durations=5"
is equivalent to running py.test --durations=5.
1.4.7 Conventions for Python test discovery
pytest implements the following standard test discovery:

• collection starts from the initial command line arguments which may be directories, filenames or test ids.
• recurse into directories, unless they match norecursedirs
• test_*.py or *_test.py files, imported by their test package name.
• Test prefixed test classes (without an __init__ method)
• test_ prefixed test functions or methods are test items
For examples of how to customize your test discovery Changing standard (Python) test discovery.

Within Python modules, pytest also discovers tests using the standard unittest.TestCase subclassing technique.

1.5 Project examples
Here are some examples of projects using pytest (please send notes via contact):
• PyPy, Python with a JIT compiler, running over 21000 tests
• the MoinMoin Wiki Engine
• sentry, realtime app-maintenance and exception tracking
• Astropy and affiliated packages
• tox, virtualenv/Hudson integration tool
• PIDA framework for integrated development
• PyPM ActiveState’s package manager
• Fom a fluid object mapper for FluidDB
• applib cross-platform utilities
• six Python 2 and 3 compatibility utilities
• pediapress MediaWiki articles
• mwlib mediawiki parser and utility library
• The Translate Toolkit for localization and conversion
• execnet rapid multi-Python deployment
• pylib cross-platform path, IO, dynamic code library
• Pacha configuration management in five minutes
• bbfreeze create standalone executables from Python scripts
• pdb++ a fancier version of PDB
• py-s3fuse Amazon S3 FUSE based filesystem
• waskr WSGI Stats Middleware
• guachi global persistent configs for Python modules
• Circuits lightweight Event Driven Framework
• pygtk-helpers easy interaction with PyGTK
• QuantumCore statusmessage and repoze openid plugin
• pydataportability libraries for managing the open web
• XIST extensible HTML/XML generator
• tiddlyweb optionally headless, extensible RESTful datastore
• fancycompleter for colorful tab-completion
• Paludis tools for Gentoo Paludis package manager
• Gerald schema comparison tool
• abjad Python API for Formalized Score control
• bu a microscopic build system
• katcp Telescope communication protocol over Twisted

• kss plugin timer

• pyudev a pure Python binding to the Linux library libudev
• pytest-localserver a plugin for pytest that provides a httpserver and smtpserver
• pytest-monkeyplus a plugin that extends monkeypatch
These projects help integrate pytest into other Python frameworks:
• pytest-django for Django
• zope.pytest for Zope and Grok
• pytest_gae for Google App Engine
• There is some work underway for Kotti, a CMS built in Pyramid/Pylons
1.5.1 Some organisations using pytest
• Square Kilometre Array, Cape Town

• Some Mozilla QA people use pytest to distribute their Selenium tests
• Tandberg
• Shootq
• Stups department of Heinrich Heine University Duesseldorf
• cellzome
• Open End, Gothenborg
• Laboratory of Bioinformatics, Warsaw
• merlinux, Germany
• many more ... (please be so kind to send a note via contact)
1.6 Some Issues and Questions
Note: This FAQ is here only mostly for historic reasons. Checkout pytest Q&A at Stackoverflow for many questions
and answers related to pytest and/or use contact channels to get help.
1.6.1 On naming, nosetests, licensing and magic
How does pytest relate to nose and unittest?
pytest and nose share basic philosophy when it comes to running and writing Python tests. In fact, you can run
many tests written for nose with pytest. nose was originally created as a clone of pytest when pytest was in
the 0.8 release cycle. Note that starting with pytest-2.0 support for running unittest test suites is majorly improved.
1.6. Some Issues and Questions 17

how does pytest relate to twisted’s trial?
Since some time pytest has builtin support for supporting tests written using trial. It does not itself start a reactor,
however, and does not handle Deferreds returned from a test in pytest style. If you are using trial’s unittest.TestCase
chances are that you can just run your tests even if you return Deferreds. In addition, there also is a dedicated pytest-
twisted plugin which allows you to return deferreds from pytest-style tests, allowing the use of pytest fixtures: explicit,
modular, scalable and other features.
how does pytest work with Django?
In 2012, some work is going into the pytest-django plugin. It substitutes the usage of Django’s manage.py test
and allows the use of all pytest features most of which are not available from Django directly.
What’s this “magic” with pytest? (historic notes)
Around 2007 (version 0.8) some people thought that pytest was using too much “magic”. It had been part of
the pylib which contains a lot of unrelated python library code. Around 2010 there was a major cleanup refactoring,
which removed unused or deprecated code and resulted in the new pytest PyPI package which strictly contains only
test-related code. This release also brought a complete pluginification such that the core is around 300 lines of code
and everything else is implemented in plugins. Thus pytest today is a small, universally runnable and customizable
testing framework for Python. Note, however, that pytest uses metaprogramming techniques and reading its source
is thus likely not something for Python beginners.
A second “magic” issue was the assert statement debugging feature. Nowadays, pytest explicitely rewrites assert
statements in test modules in order to provide more useful assert feedback. This completely avoids previous issues of
confusing assertion-reporting. It also means, that you can use Python’s -O optimization without losing assertions in
test modules.
pytest contains a second, mostly obsolete, assert debugging technique, invoked via --assert=reinterpret,
activated by default on Python-2.5: When an assert statement fails, pytest re-interprets the expression part to
show intermediate values. This technique suffers from a caveat that the rewriting does not: If your expression has side
effects (better to avoid them anyway!) the intermediate values may not be the same, confusing the reinterpreter and
obfuscating the initial error (this is also explained at the command line if it happens).
You can also turn off all assertion interaction using the --assertmode=off option.
Why a py.test instead of a pytest command?
Some of the reasons are historic, others are practical. pytest used to be part of the py package which provided
several developer utilities, all starting with py.<TAB>, thus providing nice TAB-completion. If you install pip
install pycmd you get these tools from a separate package. These days the command line tool could be called
pytest but since many people have gotten used to the old name and there is another tool named “pytest” we just
decided to stick with py.test for now.
1.6.2 pytest fixtures, parametrized tests
Is using pytest fixtures versus xUnit setup a style question?
For simple applications and for people experienced with nose or unittest-style test setup using xUnit style setup
probably feels natural. For larger test suites, parametrized testing or setup of complex test resources using funcargs

may feel more natural. Moreover, funcargs are ideal for writing advanced test support code (like e.g. the monkey-
patch, the tmpdir or capture funcargs) because the support code can register setup/teardown functions in a managed
class/module/function scope.
Can I yield multiple values from a fixture function function?
There are two conceptual reasons why yielding from a factory function is not possible:
• If multiple factories yielded values there would be no natural place to determine the combination policy - in
real-world examples some combinations often should not run.
• Calling factories for obtaining test function arguments is part of setting up and running a test. At that point it is
not possible to add new test calls to the test collection anymore.
However, with pytest-2.3 you can use the Fixtures as Function arguments decorator and specify params so that all
tests depending on the factory-created resource will run multiple times with different parameters.
You can also use the pytest_generate_tests hook to implement the parametrization scheme of your choice.
1.6.3 pytest interaction with other packages
Issues with pytest, multiprocess and setuptools?
On Windows the multiprocess package will instantiate sub processes by pickling and thus implicitly re-import a lot
of local modules. Unfortunately, setuptools-0.6.11 does not if __name__==’__main__’ protect its generated
command line script. This leads to infinite recursion when running a test that instantiates Processes.
As of mid-2013, there shouldn’t be a problem anymore when you use the standard setuptools (note that distribute has
been merged back into setuptools which is now shipped directly with virtualenv).
1.6. Some Issues and Questions 19


CHAPTER
TWO
PYTEST REFERENCE DOCUMENTATION
2.1 Pytest API and builtin fixtures
This is a list of pytest.* API functions and fixtures.

For information on plugin hooks and objects, see Working with plugins and conftest files.
For information on the pytest.mark mechanism, see Marking test functions with attributes.
For the below objects, you can also interactively ask for help, e.g. by typing on the Python interactive prompt some-
thing like:
import pytest
help(pytest)
2.1.1 Invoking pytest interactively
main(args=None, plugins=None)
return exit code, after performing an in-process test run.
Parameters
• args – list of command line arguments.
• plugins – list of plugin objects to be auto-registered during initialization.
More examples at Calling pytest from Python code
2.1.2 Helpers for assertions about Exceptions/Warnings
raises(ExpectedException, *args, **kwargs)

assert that a code block/function call raises @ExpectedException and raise a failure exception otherwise.
This helper produces a py.code.ExceptionInfo() object.
If using Python 2.5 or above, you may use this function as a context manager:
>>> with raises(ZeroDivisionError):
... 1/0
Or you can specify a callable by passing a to-be-called lambda:

>>> raises(ZeroDivisionError, lambda: 1/0)
<ExceptionInfo ...>
21
or you can specify an arbitrary callable with arguments:

>>> def f(x): return 1/x
...
>>> raises(ZeroDivisionError, f, 0)
<ExceptionInfo ...>
>>> raises(ZeroDivisionError, f, x=0)
<ExceptionInfo ...>
A third possibility is to use a string to be executed:

>>> raises(ZeroDivisionError, "f(0)")
<ExceptionInfo ...>
Note: Performance note:

Similar to caught exception objects in Python, explicitly clearing local references to returned
py.code.ExceptionInfo objects can help the Python interpreter speed up its garbage collection.
Clearing those references breaks a reference cycle (ExceptionInfo –> caught exception –> frame stack
raising the exception –> current frame stack –> local variables –> ExceptionInfo) which makes Python
keep all objects referenced from that cycle (including all local variables in the current frame) alive until the
next cyclic garbage collection run. See the official Python try statement documentation for more detailed
information.
Examples at Assertions about expected exceptions.

deprecated_call(func, *args, **kwargs)
assert that calling func(*args, **kwargs) triggers a DeprecationWarning.
2.1.3 Raising a specific test outcome
You can use the following functions in your test, fixture or setup functions to force a certain test outcome. Note that
most often you can rather use declarative marks, see Skip and xfail: dealing with tests that can not succeed.
fail(msg=’‘, pytrace=True)
explicitely fail an currently-executing test with the given Message.
Parameters pytrace – if false the msg represents the full failure information and no python trace-
back will be reported.
skip(msg=’‘)
skip an executing test with the given message. Note: it’s usually better to use the pytest.mark.skipif marker
to declare a test to be skipped under certain conditions like mismatching platforms or dependencies. See the
pytest_skipping plugin for details.
importorskip(modname, minversion=None)
return imported module if it has at least “minversion” as its __version__ attribute. If no minversion is specified
the a skip is only triggered if the module can not be imported. Note that version comparison only works with
simple version strings like “1.2.3” but not “1.2.3.dev1” or others.
xfail(reason=’‘)
xfail an executing test or setup functions with the given reason.
exit(msg)
exit testing process as if KeyboardInterrupt was triggered.
22 Chapter 2. pytest reference documentation

2.1.4 fixtures and requests
To mark a fixture function:

fixture(scope=’function’, params=None, autouse=False, ids=None)
(return a) decorator to mark a fixture factory function.
This decorator can be used (with or or without parameters) to define a fixture function. The name of the fixture
function can later be referenced to cause its invocation ahead of running tests: test modules or classes can use the
pytest.mark.usefixtures(fixturename) marker. Test functions can directly use fixture names as input arguments
in which case the fixture instance returned from the fixture function will be injected.
Parameters
• scope – the scope for which this fixture is shared, one of “function” (default), “class”,
“module”, “session”.
• params – an optional list of parameters which will cause multiple invocations of the fixture
function and all of the tests using it.
• autouse – if True, the fixture func is activated for all tests that can see it. If False (the
default) then an explicit reference is needed to activate the fixture.
• ids – list of string ids each corresponding to the params so that they are part of the test id.
If no ids are provided they will be generated automatically from the params.
Tutorial at pytest fixtures: explicit, modular, scalable.
The request object that can be used from fixture functions.
class FixtureRequest
A request for a fixture from a test or fixture function.
A request object gives access to the requesting test context and has an optional param attribute in case the
fixture is parametrized indirectly.
fixturename = None
fixture for which this request is being performed
scope = None
Scope string, one of “function”, “cls”, “module”, “session”
node
underlying collection node (depends on current request scope)
config
the pytest config object associated with this request.
function
test function object if the request has a per-function scope.
cls
class (can be None) where the test function was collected.
instance
instance (can be None) on which test function was collected.
module
python module object where the test function was collected.
fspath
the file system path of the test module which collected this test.
2.1. Pytest API and builtin fixtures 23

keywords
keywords/markers dictionary for the underlying node.
session
pytest session object.
addfinalizer(finalizer)
add finalizer/teardown function to be called after the last test within the requesting test context finished
execution.
applymarker(marker)
Apply a marker to a single test function invocation. This method is useful if you don’t want to have a
keyword/marker on all function invocations.
Parameters marker – a _pytest.mark.MarkDecorator object created by a call to
pytest.mark.NAME(...).
raiseerror(msg)
raise a FixtureLookupError with the given message.
cached_setup(setup, teardown=None, scope=’module’, extrakey=None)
(deprecated) Return a testing resource managed by setup & teardown calls. scope and extrakey
determine when the teardown function will be called so that subsequent calls to setup would recreate
the resource. With pytest-2.3 you often do not need cached_setup() as you can directly declare a
scope on a fixture function and register a finalizer through request.addfinalizer().
Parameters
• teardown – function receiving a previously setup resource.
• setup – a no-argument function creating a resource.
• scope – a string value out of function, class, module or session indicating the
caching lifecycle of the resource.
• extrakey – added to internal caching key of (funcargname, scope).
getfuncargvalue(argname)
Dynamically retrieve a named fixture function argument.
As of pytest-2.3, it is easier and usually better to access other fixture values by stating it as an input
argument in the fixture function. If you only can decide about using another fixture at test setup time, you
may use this function to retrieve it inside a fixture function body.
2.1.5 Builtin fixtures/function arguments
You can ask for available builtin or project-custom fixtures by typing:

$ py.test -q --fixtures
capsys
enables capturing of writes to sys.stdout/sys.stderr and makes
captured output available via ``capsys.readouterr()`` method calls
which return a ``(out, err)`` tuple.
capfd
enables capturing of writes to file descriptors 1 and 2 and makes
captured output available via ``capfd.readouterr()`` method calls
which return a ``(out, err)`` tuple.
monkeypatch
The returned ``monkeypatch`` funcarg provides these
helper methods to modify objects, dictionaries or os.environ::

monkeypatch.setattr(obj, name, value, raising=True)

monkeypatch.delattr(obj, name, raising=True)
monkeypatch.setitem(mapping, name, value)
monkeypatch.delitem(obj, name, raising=True)
monkeypatch.setenv(name, value, prepend=False)
monkeypatch.delenv(name, value, raising=True)
monkeypatch.syspath_prepend(path)
monkeypatch.chdir(path)
All modifications will be undone after the requesting

test function has finished. The ``raising``
parameter determines if a KeyError or AttributeError
will be raised if the set/deletion operation has no target.
pytestconfig
the pytest config object with access to command line opts.
recwarn
Return a WarningsRecorder instance that provides these methods:
* ``pop(category=None)``: return last warning matching the category.

* ``clear()``: clear list of warnings
See http://docs.python.org/library/warnings.html for information

on warning categories.
tmpdir
return a temporary directory path object
which is unique to each test function invocation,
created as a sub directory of the base temporary
directory. The returned object is a `py.path.local`_
path object.
in 0.00 seconds
2.2 Basic test configuration
2.2.1 Command line options and configuration file settings
You can get help on command line options and values in INI-style configurations files by using the general help option:
py.test -h # prints options _and_ config file settings
This will display command line and configuration file settings which were registered by installed plugins.
2.2.2 initialization: determining rootdir and inifile
New in version 2.7.

pytest determines a “rootdir” for each test run which depends on the command line arguments (specified test files,
paths) and on the existence of inifiles. The determined rootdir and ini-file are printed as part of the pytest header. The
rootdir is used for constructing “nodeids” during collection and may also be used by plugins to store project/testrun-
specific information.
Here is the algorithm which finds the rootdir from args:
• determine the common ancestor directory for the specified args.
2.2. Basic test configuration 25

• look for pytest.ini, tox.ini and setup.cfg files in the ancestor directory and upwards. If one is
matched, it becomes the ini-file and its directory becomes the rootdir. An existing pytest.ini file will always
be considered a match whereas tox.ini and setup.cfg will only match if they contain a [pytest]
section.
• if no ini-file was found, look for setup.py upwards from the common ancestor directory to determine the
rootdir.
• if no ini-file and no setup.py was found, use the already determined common ancestor as root directory.
This allows to work with pytest in structures that are not part of a package and don’t have any particular ini-file
configuration.
Note that options from multiple ini-files candidates are never merged, the first one wins (pytest.ini always wins
even if it does not contain a [pytest] section).
The config object will subsequently carry these attributes:
• config.rootdir: the determined root directory, guaranteed to exist.
• config.inifile: the determined ini-file, may be None.
The rootdir is used a reference directory for constructing test addresses (“nodeids”) and can be used also by plugins
for storing per-testrun information.
Example:
py.test path/to/testdir path/other/
will determine the common ancestor as path and then check for ini-files as follows:
# first look for pytest.ini files
path/pytest.ini
path/setup.cfg # must also contain [pytest] section to match
path/tox.ini # must also contain [pytest] section to match
pytest.ini
... # all the way down to the root
# now look for setup.py

path/setup.py
setup.py
... # all the way down to the root
2.2.3 How to change command line options defaults
It can be tedious to type the same series of command line options every time you use pytest. For example, if you
always want to see detailed info on skipped and xfailed tests, as well as have terser “dot” progress output, you can
write it into a configuration file:
# content of pytest.ini
# (or tox.ini or setup.cfg)
[pytest]
addopts = -rsxX -q
Alternatively, you can set a PYTEST_ADDOPTS environment variable to add command line options while the envi-
ronment is in use:
export PYTEST_ADDOPTS="-rsxX -q"
From now on, running pytest will add the specified options.

2.2.4 Builtin configuration file options
minversion
Specifies a minimal pytest version required for running tests.
minversion = 2.1 # will fail if we run with pytest-2.0
addopts
Add the specified OPTS to the set of command line arguments as if they had been specified by the user. Example:
if you have this ini file content:
[pytest]
addopts = --maxfail=2 -rf # exit after 2 failures, report fail info
issuing py.test test_hello.py actually means:

py.test --maxfail=2 -rf test_hello.py
Default is to add no options.

norecursedirs
Set the directory basename patterns to avoid when recursing for test discovery. The individual (fnmatch-style)
patterns are applied to the basename of a directory to decide if to recurse into it. Pattern matching characters:
* matches everything
? matches any single character
[seq] matches any character in seq
[!seq] matches any char not in seq
Default patterns are ’.*’, ’CVS’, ’_darcs’, ’{arch}’, ’*.egg’. Setting a norecursedirs
replaces the default. Here is an example of how to avoid certain directories:
# content of setup.cfg
[pytest]
norecursedirs = .svn _build tmp*
This would tell pytest to not look into typical subversion or sphinx-build directories or into any tmp prefixed
directory.
python_files
One or more Glob-style file patterns determining which python files are considered as test modules.
python_classes
One or more name prefixes or glob-style patterns determining which classes are considered for test collection.
Here is an example of how to collect tests from classes that end in Suite:
[pytest]
python_classes = *Suite
Note that unittest.TestCase derived classes are always collected regardless of this option, as
unittest‘s own collection framework is used to collect those tests.
python_functions
One or more name prefixes or glob-patterns determining which test functions and methods are considered tests.
Here is an example of how to collect test functions and methods that end in _test:
[pytest]
python_functions = *_test
2.2. Basic test configuration 27

Note that this has no effect on methods that live on a unittest .TestCase derived class, as unittest‘s
own collection framework is used to collect those tests.
See Changing naming conventions for more detailed examples.
doctest_optionflags
One or more doctest flag names from the standard doctest module. See how py.test handles doctests.
2.3 The writing and reporting of assertions in tests
2.3.1 Asserting with the assert statement
pytest allows you to use the standard python assert for verifying expectations and values in Python tests. For
example, you can write the following:
# content of test_assert1.py
def f():
return 3
assert f() == 4
to assert that your function returns a certain value. If this assertion fails you will see the return value of the function
call:
$ py.test test_assert1.py
collected 1 items
test_assert1.py F
================================= FAILURES =================================

______________________________ test_function _______________________________
> assert f() == 4
E assert 3 == 4
E + where 3 = f()
test_assert1.py:5: AssertionError
pytest has support for showing the values of the most common subexpressions including calls, attributes, compar-
isons, and binary and unary operators. (See Demo of Python failure reports with pytest). This allows you to use the
idiomatic python constructs without boilerplate code while not losing introspection information.
However, if you specify a message with the assertion like this:
assert a % 2 == 0, "value was odd, should be even"
then no assertion introspection takes places at all and the message will be simply shown in the traceback.
See Advanced assertion introspection for more information on assertion introspection.

2.3.2 Assertions about expected exceptions
In order to write assertions about raised exceptions, you can use pytest.raises as a context manager like this:
import pytest
def test_zero_division():
with pytest.raises(ZeroDivisionError):
1 / 0
and if you need to have access to the actual exception info you may use:
def test_recursion_depth():
with pytest.raises(RuntimeError) as excinfo:
def f():
f()
f()
assert 'maximum recursion' in str(excinfo.value)
excinfo is a py.code.ExceptionInfo instance, which is a wrapper around the actual exception raised. The main
attributes of interest are .type, .value and .traceback.
If you want to write test code that works on Python 2.4 as well, you may also use two other ways to test for an expected
exception:
pytest.raises(ExpectedException, func, *args, **kwargs)
pytest.raises(ExpectedException, "func(*args, **kwargs)")
both of which execute the specified function with args and kwargs and asserts that the given ExpectedException
is raised. The reporter will provide you with helpful output in case of failures such as no exception or wrong exception.
Note that it is also possible to specify a “raises” argument to pytest.mark.xfail, which checks that the test is
failing in a more specific way than just having any exception raised:
@pytest.mark.xfail(raises=IndexError)
def test_f():
f()
Using pytest.raises is likely to be better for cases where you are testing exceptions your own code is deliber-
ately raising, whereas using @pytest.mark.xfail with a check function is probably better for something like
documenting unfixed bugs (where the test describes what “should” happen) or bugs in dependencies.
2.3.3 Making use of context-sensitive comparisons
New in version 2.0.

pytest has rich support for providing context-sensitive information when it encounters comparisons. For example:
# content of test_assert2.py
def test_set_comparison():
set1 = set("1308")
set2 = set("8035")
assert set1 == set2
if you run this module:

$ py.test test_assert2.py
2.3. The writing and reporting of assertions in tests 29


collected 1 items
test_assert2.py F
================================= FAILURES =================================

___________________________ test_set_comparison ____________________________
def test_set_comparison():
set1 = set("1308")
set2 = set("8035")
> assert set1 == set2
E assert set(['0', '1', '3', '8']) == set(['0', '3', '5', '8'])
E Extra items in the left set:
E '1'
E Extra items in the right set:
E '5'
E Use -v to get the full diff
test_assert2.py:5: AssertionError
Special comparisons are done for a number of cases:

• comparing long strings: a context diff is shown
• comparing long sequences: first failing indices
• comparing dicts: different entries
See the reporting demo for many more examples.
2.3.4 Defining your own assertion comparison
It is possible to add your own detailed explanations by implementing the pytest_assertrepr_compare hook.
pytest_assertrepr_compare(config, op, left, right)
return explanation for comparisons in failing assert expressions.
Return None for no custom explanation, otherwise return a list of strings. The strings will be joined by newlines
but any newlines in a string will be escaped. Note that all but the first line will be indented sligthly, the intention
is for the first line to be a summary.
As an example consider adding the following hook in a conftest.py which provides an alternative explanation for Foo
objects:
# content of conftest.py
from test_foocompare import Foo
def pytest_assertrepr_compare(op, left, right):
if isinstance(left, Foo) and isinstance(right, Foo) and op == "==":
return ['Comparing Foo instances:',
' vals: %s != %s' % (left.val, right.val)]
now, given this test module:

# content of test_foocompare.py
class Foo:
def __init__(self, val):
self.val = val

def test_compare():
f1 = Foo(1)
f2 = Foo(2)
assert f1 == f2
you can run the test module and get the custom output defined in the conftest file:
$ py.test -q test_foocompare.py
F
================================= FAILURES =================================
_______________________________ test_compare _______________________________
def test_compare():
f1 = Foo(1)
f2 = Foo(2)
> assert f1 == f2
E assert Comparing Foo instances:
E vals: 1 != 2
test_foocompare.py:8: AssertionError
2.3.5 Advanced assertion introspection
New in version 2.1.

Reporting details about a failing assertion is achieved either by rewriting assert statements before they are run or
re-evaluating the assert expression and recording the intermediate values. Which technique is used depends on the
location of the assert, pytest configuration, and Python version being used to run pytest. Note that for assert
statements with a manually provided message, i.e. assert expr, message, no assertion introspection takes
place and the manually provided message will be rendered in tracebacks.
By default, if the Python version is greater than or equal to 2.6, pytest rewrites assert statements in test modules.
Rewritten assert statements put introspection information into the assertion failure message. pytest only rewrites test
modules directly discovered by its test collection process, so asserts in supporting modules which are not themselves
test modules will not be rewritten.
Note: pytest rewrites test modules on import. It does this by using an import hook to write a new pyc files. Most of
the time this works transparently. However, if you are messing with import yourself, the import hook may interfere. If
this is the case, simply use --assert=reinterp or --assert=plain. Additionally, rewriting will fail silently
if it cannot write new pycs, i.e. in a read-only filesystem or a zipfile.
If an assert statement has not been rewritten or the Python version is less than 2.6, pytest falls back on assert
reinterpretation. In assert reinterpretation, pytest walks the frame of the function containing the assert statement
to discover sub-expression results of the failing assert statement. You can force pytest to always use assertion
reinterpretation by passing the --assert=reinterp option.
Assert reinterpretation has a caveat not present with assert rewriting: If evaluating the assert expression has side effects
you may get a warning that the intermediate values could not be determined safely. A common example of this issue
is an assertion which reads from a file:
assert f.read() != '...'
If this assertion fails then the re-evaluation will probably succeed! This is because f.read() will return an empty
string when it is called the second time during the re-evaluation. However, it is easy to rewrite the assertion and avoid
any trouble:
2.3. The writing and reporting of assertions in tests 31

content = f.read()
assert content != '...'
All assert introspection can be turned off by passing --assert=plain.

For further information, Benjamin Peterson wrote up Behind the scenes of pytest’s new assertion rewriting.
New in version 2.1: Add assert rewriting as an alternate introspection technique.
Changed in version 2.1: Introduce the --assert option. Deprecate --no-assert and --nomagic.
2.4 pytest fixtures: explicit, modular, scalable
New in version 2.0/2.3/2.4.

The purpose of test fixtures is to provide a fixed baseline upon which tests can reliably and repeatedly execute. pytest
fixtures offer dramatic improvements over the classic xUnit style of setup/teardown functions:
• fixtures have explicit names and are activated by declaring their use from test functions, modules, classes or
whole projects.
• fixtures are implemented in a modular manner, as each fixture name triggers a fixture function which can itself
use other fixtures.
• fixture management scales from simple unit to complex functional testing, allowing to parametrize fixtures and
tests according to configuration and component options, or to re-use fixtures across class, module or whole test
session scopes.
In addition, pytest continues to support classic xunit-style setup. You can mix both styles, moving incrementally from
classic to new style, as you prefer. You can also start out from existing unittest.TestCase style or nose based projects.
Note: pytest-2.4 introduced an additional experimental yield fixture mechanism for easier context manager integration
and more linear writing of teardown code.
2.4.1 Fixtures as Function arguments
Test functions can receive fixture objects by naming them as an input argument. For each argument name, a fix-
ture function with that name provides the fixture object. Fixture functions are registered by marking them with
@pytest.fixture. Let’s look at a simple self-contained test module containing a fixture and a test function
using it:
# content of ./test_smtpsimple.py
import pytest
@pytest.fixture
def smtp():
import smtplib
return smtplib.SMTP("merlinux.eu")
def test_ehlo(smtp):
response, msg = smtp.ehlo()
assert response == 250
assert 0 # for demo purposes
Here, the test_ehlo needs the smtp fixture value. pytest will discover and call the @pytest.fixture marked
smtp fixture function. Running the test looks like this:

$ py.test test_smtpsimple.py
collected 1 items
test_smtpsimple.py F
================================= FAILURES =================================

________________________________ test_ehlo _________________________________
smtp = <smtplib.SMTP object at 0x7f9d45764c88>
response, msg = smtp.ehlo()
assert response == 250
> assert 0 # for demo purposes
E assert 0
test_smtpsimple.py:11: AssertionError
In the failure traceback we see that the test function was called with a smtp argument, the smtplib.SMTP()
instance created by the fixture function. The test function fails on our deliberate assert 0. Here is the exact
protocol used by pytest to call the test function this way:
1. pytest finds the test_ehlo because of the test_ prefix. The test function needs a function argument named
smtp. A matching fixture function is discovered by looking for a fixture-marked function named smtp.
2. smtp() is called to create an instance.
3. test_ehlo(<SMTP instance>) is called and fails in the last line of the test function.
Note that if you misspell a function argument or want to use one that isn’t available, you’ll see an error with a list of
available function arguments.
Note: You can always issue:

py.test --fixtures test_simplefactory.py
to see available fixtures.

In versions prior to 2.3 there was no @pytest.fixture marker and you had to use a magic
pytest_funcarg__NAME prefix for the fixture factory. This remains and will remain supported but is not anymore
advertised as the primary means of declaring fixture functions.
2.4.2 “Funcargs” a prime example of dependency injection
When injecting fixtures to test functions, pytest-2.0 introduced the term “funcargs” or “funcarg mechanism” which
continues to be present also in docs today. It now refers to the specific case of injecting fixture values as arguments
to test functions. With pytest-2.3 there are more possibilities to use fixtures but “funcargs” remain as the main way as
they allow to directly state the dependencies of a test function.
As the following examples show in more detail, funcargs allow test functions to easily receive and work against specific
pre-initialized application objects without having to care about import/setup/cleanup details. It’s a prime example of
dependency injection where fixture functions take the role of the injector and test functions are the consumers of
fixture objects.
2.4. pytest fixtures: explicit, modular, scalable 33

2.4.3 Sharing a fixture across tests in a module (or class/session)
Fixtures requiring network access depend on connectivity and are usually time-expensive to create. Extending the
previous example, we can add a scope=’module’ parameter to the @pytest.fixture invocation to cause the
decorated smtp fixture function to only be invoked once per test module. Multiple test functions in a test module
will thus each receive the same smtp fixture instance. The next example puts the fixture function into a separate
conftest.py file so that tests from multiple test modules in the directory can access the fixture function:
import pytest
import smtplib
@pytest.fixture(scope="module")
def smtp():
return smtplib.SMTP("merlinux.eu")
The name of the fixture again is smtp and you can access its result by listing the name smtp as an input parameter in
any test or fixture function (in or below the directory where conftest.py is located):
# content of test_module.py
response = smtp.ehlo()
assert response[0] == 250
assert "merlinux" in response[1]
def test_noop(smtp):
response = smtp.noop()
We deliberately insert failing assert 0 statements in order to inspect what is going on and can now run the tests:
$ py.test test_module.py
collected 2 items
test_module.py FF
================================= FAILURES =================================

________________________________ test_ehlo _________________________________
smtp = <smtplib.SMTP object at 0x7fb558b12240>
> assert "merlinux" in response[1]
E TypeError: Type str doesn't support the buffer API
test_module.py:5: TypeError
________________________________ test_noop _________________________________
smtp = <smtplib.SMTP object at 0x7fb558b12240>

E assert 0
test_module.py:11: AssertionError
You see the two assert 0 failing and more importantly you can also see that the same (module-scoped) smtp
object was passed into the two test functions because pytest shows the incoming argument values in the traceback. As
a result, the two test functions using smtp run as quick as a single one because they reuse the same instance.
If you decide that you rather want to have a session-scoped smtp instance, you can simply declare it:
@pytest.fixture(scope="session")
def smtp(...):
# the returned fixture value will be shared for
# all tests needing it
2.4.4 fixture finalization / executing teardown code
pytest supports execution of fixture specific finalization code when the fixture goes out of scope. By accepting a
request object into your fixture function you can call its request.addfinalizer one or multiple times:
import smtplib
import pytest
def smtp(request):
smtp = smtplib.SMTP("merlinux.eu")
def fin():
print ("teardown smtp")
smtp.close()
request.addfinalizer(fin)
return smtp # provide the fixture value
The fin function will execute when the last test using the fixture in the module has finished execution.
Let’s execute it:
$ py.test -s -q --tb=no
FFteardown smtp
We see that the smtp instance is finalized after the two tests finished execution. Note that if we decorated our fixture
function with scope=’function’ then fixture setup and cleanup would occur around each single test. In either
case the test module itself does not need to change or know about these details of fixture setup.
2.4.5 Fixtures can introspect the requesting test context
Fixture function can accept the request object to introspect the “requesting” test function, class or module context.
Further extending the previous smtp fixture example, let’s read an optional server URL from the test module which
uses our fixture:

import pytest
import smtplib
def smtp(request):
server = getattr(request.module, "smtpserver", "merlinux.eu")
smtp = smtplib.SMTP(server)
def fin():
print ("finalizing %s (%s)" % (smtp, server))
smtp.close()
return smtp
We use the request.module attribute to optionally obtain an smtpserver attribute from the test module. If we
just execute again, nothing much has changed:
$ py.test -s -q --tb=no
FF
Let’s quickly create another test module that actually sets the server URL in its module namespace:
# content of test_anothersmtp.py
smtpserver = "mail.python.org" # will be read by smtp fixture
def test_showhelo(smtp):
assert 0, smtp.helo()
Running it:
$ py.test -qq --tb=short test_anothersmtp.py
F
================================= FAILURES =================================
______________________________ test_showhelo _______________________________
test_anothersmtp.py:5: in test_showhelo
assert 0, smtp.helo()
E AssertionError: (250, b'mail.python.org')
E assert 0
voila! The smtp fixture function picked up our mail server name from the module namespace.
2.4.6 Parametrizing a fixture
Fixture functions can be parametrized in which case they will be called multiple times, each time executing the set
of dependent tests, i. e. the tests that depend on this fixture. Test functions do usually not need to be aware of their
re-running. Fixture parametrization helps to write exhaustive functional tests for components which themselves can
be configured in multiple ways.
Extending the previous example, we can flag the fixture to create two smtp fixture instances which will cause all tests
using the fixture to run twice. The fixture function gets access to each parameter through the special request object:
import pytest
import smtplib

@pytest.fixture(scope="module",
params=["merlinux.eu", "mail.python.org"])
def smtp(request):
smtp = smtplib.SMTP(request.param)
def fin():
print ("finalizing %s" % smtp)
smtp.close()
return smtp
The main change is the declaration of params with @pytest.fixture, a list of values for each of which the
fixture function will execute and can access a value via request.param. No test function code needs to change.
So let’s just do another run:
$ py.test -q test_module.py
FFFF
================================= FAILURES =================================
__________________________ test_ehlo[merlinux.eu] __________________________
smtp = <smtplib.SMTP object at 0x7f4eecf92080>
__________________________ test_noop[merlinux.eu] __________________________
E assert 0
________________________ test_ehlo[mail.python.org] ________________________
-------------------------- Captured stdout setup ---------------------------
finalizing <smtplib.SMTP object at 0x7f4eecf92080>
________________________ test_noop[mail.python.org] ________________________


E assert 0
We see that our two test functions each ran twice, against the different smtp instances. Note also, that with the
mail.python.org connection the second test fails in test_ehlo because a different server string is expected
than what arrived.
pytest will build a string that is the test ID for each fixture value in a parametrized fixture, e.g.
test_ehlo[merlinux.eu] and test_ehlo[mail.python.org] in the above examples. These IDs can
be used with -k to select specific cases to run, and they will also identify the specific case when one is failing.
Running pytest with --collect-only will show the generated IDs.
Numbers, strings, booleans and None will have their usual string representation used in the test ID. For other objects,
pytest will make a string based on the argument name. It is possible to customise the string used in a test ID for a
certain fixture value by using the ids keyword argument:
import pytest
@pytest.fixture(params=[0, 1], ids=["spam", "ham"])

def a(request):
return request.param
def test_a(a):
pass
def idfn(fixture_value):
if fixture_value == 0:
return "eggs"
else:
return None
@pytest.fixture(params=[0, 1], ids=idfn)

def b(request):
def test_b(b):
pass
The above shows how ids can be either a list of strings to use or a function which will be called with the fixture value
and then has to return a string to use. In the latter case if the function return None then pytest’s auto-generated ID will
be used.
Running the above tests results in the following test IDs being used:
$ py.test --collect-only
collected 6 items
<Module 'test_anothersmtp.py'>
<Function 'test_showhelo[merlinux.eu]'>
<Function 'test_showhelo[mail.python.org]'>
<Module 'test_module.py'>
<Function 'test_ehlo[merlinux.eu]'>
<Function 'test_noop[merlinux.eu]'>

<Function 'test_ehlo[mail.python.org]'>
<Function 'test_noop[mail.python.org]'>
============================= in 0.02 seconds =============================
2.4.7 Modularity: using fixtures from a fixture function
You can not only use fixtures in test functions but fixture functions can use other fixtures themselves. This contributes
to a modular design of your fixtures and allows re-use of framework-specific fixtures across many projects. As a
simple example, we can extend the previous example and instantiate an object app where we stick the already defined
smtp resource into it:
# content of test_appsetup.py
import pytest
class App:
def __init__(self, smtp):
self.smtp = smtp
def app(smtp):
return App(smtp)
def test_smtp_exists(app):
assert app.smtp
Here we declare an app fixture which receives the previously defined smtp fixture and instantiates an App object
with it. Let’s run it:
$ py.test -v test_appsetup.py
platform linux -- Python 3.4.1 -- py-1.4.27 -- pytest-2.7.1 -- /tmp/sandbox/pytest/.tox/regen/bin/pyt
collecting ... collected 2 items
test_appsetup.py::test_smtp_exists[merlinux.eu] PASSED
test_appsetup.py::test_smtp_exists[mail.python.org] PASSED
========================= 2 passed in 1.09 seconds =========================
Due to the parametrization of smtp the test will run twice with two different App instances and respective smtp
servers. There is no need for the app fixture to be aware of the smtp parametrization as pytest will fully analyse the
fixture dependency graph.
Note, that the app fixture has a scope of module and uses a module-scoped smtp fixture. The example would still
work if smtp was cached on a session scope: it is fine for fixtures to use “broader” scoped fixtures but not the
other way round: A session-scoped fixture could not use a module-scoped one in a meaningful way.
2.4.8 Automatic grouping of tests by fixture instances
pytest minimizes the number of active fixtures during test runs. If you have a parametrized fixture, then all the tests
using it will first execute with one instance and then finalizers are called before the next fixture instance is created.
Among other things, this eases testing of applications which create and use global state.

The following example uses two parametrized funcargs, one of which is scoped on a per-module basis, and all the
functions perform print calls to show the setup/teardown flow:
import pytest
@pytest.fixture(scope="module", params=["mod1", "mod2"])

def modarg(request):
param = request.param
print ("create", param)
def fin():
print ("fin %s" % param)
return param
@pytest.fixture(scope="function", params=[1,2])
def otherarg(request):
def test_0(otherarg):
print (" test0", otherarg)
def test_1(modarg):
print (" test1", modarg)
def test_2(otherarg, modarg):
print (" test2", otherarg, modarg)
Let’s run the tests in verbose mode and with looking at the print-output:
$ py.test -v -s test_module.py
test_module.py::test_0[1] test0 1
PASSED
test_module.py::test_0[2] test0 2
PASSED
test_module.py::test_1[mod1] create mod1
test1 mod1
PASSED
test_module.py::test_2[1-mod1] test2 1 mod1
PASSED
PASSED
test_module.py::test_1[mod2] create mod2
test1 mod2
PASSED
PASSED
PASSED
You can see that the parametrized module-scoped modarg resource caused an ordering of test execution that lead
to the fewest possible “active” resources. The finalizer for the mod1 parametrized resource was executed before the
mod2 resource was setup.

2.4.9 using fixtures from classes, modules or projects
Sometimes test functions do not directly need access to a fixture object. For example, tests may require to operate
with an empty directory as the current working directory but otherwise do not care for the concrete directory. Here is
how you can can use the standard tempfile and pytest fixtures to achieve it. We separate the creation of the fixture into
a conftest.py file:
import pytest
import tempfile
import os
@pytest.fixture()
def cleandir():
newpath = tempfile.mkdtemp()
os.chdir(newpath)
and declare its use in a test module via a usefixtures marker:

# content of test_setenv.py
import os
import pytest
@pytest.mark.usefixtures("cleandir")
class TestDirectoryInit:
def test_cwd_starts_empty(self):
assert os.listdir(os.getcwd()) == []
with open("myfile", "w") as f:
f.write("hello")
def test_cwd_again_starts_empty(self):
assert os.listdir(os.getcwd()) == []
Due to the usefixtures marker, the cleandir fixture will be required for the execution of each test method, just
as if you specified a “cleandir” function argument to each of them. Let’s run it to verify our fixture is activated and the
tests pass:
$ py.test -q
..
You can specify multiple fixtures like this:

@pytest.mark.usefixtures("cleandir", "anotherfixture")
and you may specify fixture usage at the test module level, using a generic feature of the mark mechanism:
pytestmark = pytest.mark.usefixtures("cleandir")
Lastly you can put fixtures required by all tests in your project into an ini-file:
[pytest]
usefixtures = cleandir

2.4.10 autouse fixtures (xUnit setup on steroids)
Occasionally, you may want to have fixtures get invoked automatically without a usefixtures or funcargs reference.
As a practical example, suppose we have a database fixture which has a begin/rollback/commit architecture and we
want to automatically surround each test method by a transaction and a rollback. Here is a dummy self-contained
implementation of this idea:
# content of test_db_transact.py
import pytest
class DB:
def __init__(self):
self.intransaction = []
def begin(self, name):
self.intransaction.append(name)
def rollback(self):
self.intransaction.pop()
def db():
return DB()
class TestClass:
@pytest.fixture(autouse=True)
def transact(self, request, db):
db.begin(request.function.__name__)
request.addfinalizer(db.rollback)
def test_method1(self, db):

assert db.intransaction == ["test_method1"]
def test_method2(self, db):

assert db.intransaction == ["test_method2"]
The class-level transact fixture is marked with autouse=true which implies that all test methods in the class will
use this fixture without a need to state it in the test function signature or with a class-level usefixtures decorator.
If we run it, we get two passing tests:
$ py.test -q
..
Here is how autouse fixtures work in other scopes:

• if an autouse fixture is defined in a test module, all its test functions automatically use it.
• if an autouse fixture is defined in a conftest.py file then all tests in all test modules belows its directory will
invoke the fixture.
• lastly, and please use that with care: if you define an autouse fixture in a plugin, it will be invoked for all tests
in all projects where the plugin is installed. This can be useful if a fixture only anyway works in the presence
of certain settings e. g. in the ini-file. Such a global fixture should always quickly determine if it should do any
work and avoid expensive imports or computation otherwise.
Note that the above transact fixture may very well be a fixture that you want to make available in your project
without having it generally active. The canonical way to do that is to put the transact definition into a conftest.py file
without using autouse:

@pytest.fixture()
def transact(self, request, db):
db.begin()
request.addfinalizer(db.rollback)
and then e.g. have a TestClass using it by declaring the need:

@pytest.mark.usefixtures("transact")
class TestClass:
def test_method1(self):
...
All test methods in this TestClass will use the transaction fixture while other test classes or functions in the module
will not use it unless they also add a transact reference.
2.4.11 Shifting (visibility of) fixture functions
If during implementing your tests you realize that you want to use a fixture function from multiple test files you can
move it to a conftest.py file or even separately installable plugins without changing test code. The discovery of fixtures
functions starts at test classes, then test modules, then conftest.py files and finally builtin and third party plugins.
2.4.12 Overriding fixtures on various levels
In relatively large test suite, you most likely need to override a global or root fixture with a locally defined
one, keeping the test code readable and maintainable.
Override a fixture on a folder (conftest) level
Given the tests file structure is:

tests/
__init__.py
conftest.py
# content of tests/conftest.py
import pytest
@pytest.fixture
def username():
return 'username'
test_something.py
# content of tests/test_something.py
def test_username(username):
assert username == 'username'
subfolder/
__init__.py
conftest.py
# content of tests/subfolder/conftest.py
import pytest
@pytest.fixture

def username(username):
return 'overridden-' + username
test_something.py
# content of tests/subfolder/test_something.py
assert username == 'overridden-username'
As you can see, a fixture with the same name can be overridden for certain test folder level. Note that the base or
super fixture can be accessed from the overriding fixture easily - used in the example above.
Override a fixture on a test module level

tests/
__init__.py
conftest.py
@pytest.fixture
def username():
return 'username'
test_something.py
import pytest
@pytest.fixture
return 'overridden-' + username
assert username == 'overridden-username'
test_something_else.py
# content of tests/test_something_else.py
import pytest
@pytest.fixture
return 'overridden-else-' + username
assert username == 'overridden-else-username'
In the example above, a fixture with the same name can be overridden for certain test module.
Override a fixture with direct test parametrization

tests/
__init__.py
conftest.py

import pytest
@pytest.fixture
def username():
return 'username'
@pytest.fixture
def other_username(username):
return 'other-' + username
test_something.py
import pytest
@pytest.mark.parametrize('username', ['directly-overridden-username'])
assert username == 'directly-overridden-username'
@pytest.mark.parametrize('username', ['directly-overridden-username-other'])
def test_username_other(other_username):
assert username == 'other-directly-overridden-username-other'
In the example above, a fixture value is overridden by the test parameter value. Note that the value of the fixture can
be overridden this way even if the test doesn’t use it directly (doesn’t mention it in the function prototype).
Override a parametrized fixture with non-parametrized one and vice versa

tests/
__init__.py
conftest.py
import pytest
@pytest.fixture(params=['one', 'two', 'three'])

def parametrized_username(request):
@pytest.fixture
def non_parametrized_username(request):
return 'username'
test_something.py
import pytest
@pytest.fixture
def parametrized_username():
return 'overridden-username'
@pytest.fixture(params=['one', 'two', 'three'])

def non_parametrized_username(request):
def test_username(parametrized_username):

assert parametrized_username == 'overridden-username'
def test_parametrized_username(non_parametrized_username):
assert non_parametrized_username in ['one', 'two', 'three']
test_something_else.py
# content of tests/test_something_else.py
def test_username(parametrized_username):
assert parametrized_username in ['one', 'two', 'three']
def test_username(non_parametrized_username):
assert non_parametrized_username == 'username'
In the example above, a parametrized fixture is overridden with a non-parametrized version, and a non-parametrized
fixture is overridden with a parametrized version for certain test module. The same applies for the test folder level
obviously.
2.5 Fixture functions using “yield” / context manager integration
New in version 2.4.

pytest-2.4 allows fixture functions to seamlessly use a yield instead of a return statement to provide a fixture
value while otherwise fully supporting all other fixture features.
Note: “yielding” fixture values is an experimental feature and its exact declaration may change later but earliest in a
2.5 release. You can thus safely use this feature in the 2.4 series but may need to adapt later. Test functions themselves
will not need to change (as a general feature, they are ignorant of how fixtures are setup).
Let’s look at a simple standalone-example using the new yield syntax:

# content of test_yield.py
import pytest
@pytest.yield_fixture
def passwd():
print ("\nsetup before yield")
f = open("/etc/passwd")
yield f.readlines()
print ("teardown after yield")
f.close()
def test_has_lines(passwd):
print ("test called")
assert passwd
In contrast to finalization through registering callbacks, our fixture function used a yield statement to provide the
lines of the /etc/passwd file. The code after the yield statement serves as the teardown code, avoiding the
indirection of registering a teardown callback function.
Let’s run it with output capturing disabled:
$ py.test -q -s test_yield.py
setup before yield

test called

.teardown after yield
We can also seamlessly use the new syntax with with statements. Let’s simplify the above passwd fixture:
# content of test_yield2.py
import pytest
@pytest.yield_fixture
def passwd():
with open("/etc/passwd") as f:
yield f.readlines()
def test_has_lines(passwd):
assert len(passwd) >= 1
The file f will be closed after the test finished execution because the Python file object supports finalization when
the with statement ends.
Note that the new syntax is fully integrated with using scope, params and other fixture features. Changing existing
fixture functions to use yield is thus straight forward.
2.5.1 Discussion and future considerations / feedback
The yield-syntax has been discussed by pytest users extensively. In general, the advantages of the using a yield
fixture syntax are:
• easy provision of fixtures in conjunction with context managers.
• no need to register a callback, providing for more synchronous control flow in the fixture function. Also there is
no need to accept the request object into the fixture function just for providing finalization code.
However, there are also limitations or foreseeable irritations:
• usually yield is used for producing multiple values. But fixture functions can only yield exactly one value.
Yielding a second fixture value will get you an error. It’s possible we can evolve pytest to allow for produc-
ing multiple values as an alternative to current parametrization. For now, you can just use the normal fixture
parametrization mechanisms together with yield-style fixtures.
• the yield syntax is similar to what contextlib.contextmanager() decorated functions provide. With
pytest fixture functions, the “after yield” part will always be invoked, independently from the exception status
of the test function which uses the fixture. The pytest behaviour makes sense if you consider that many different
test functions might use a module or session scoped fixture. Some test functions might raise exceptions and
others not, so how could pytest re-raise a single exception at the yield point in the fixture function?
• lastly yield introduces more than one way to write fixture functions, so what’s the obvious way to a newcomer?
Newcomers reading the docs will see feature examples using the return style so should use that, if in doubt.
Others can start experimenting with writing yield-style fixtures and possibly help evolving them further.
If you want to feedback or participate in the ongoing discussion, please join our contact channels. you are most
welcome.
2.6 Parametrizing fixtures and test functions
pytest supports test parametrization in several well-integrated ways:
2.6. Parametrizing fixtures and test functions 47

• pytest.fixture() allows to define parametrization at the level of fixture functions.

• @pytest.mark.parametrize allows to define parametrization at the function or class level, provides multiple
argument/fixture sets for a particular test function or class.
• pytest_generate_tests enables implementing your own custom dynamic parametrization scheme or extensions.
2.6.1 @pytest.mark.parametrize: parametrizing test functions
New in version 2.2,: improved in 2.4

The builtin pytest.mark.parametrize decorator enables parametrization of arguments for a test function. Here
is a typical example of a test function that implements checking that a certain input leads to an expected output:
# content of test_expectation.py
import pytest
@pytest.mark.parametrize("input,expected", [
("3+5", 8),
("2+4", 6),
("6*9", 42),
])
def test_eval(input, expected):
assert eval(input) == expected
Here, the @parametrize decorator defines three different (input,expected) tuples so that the test_eval
function will run three times using them in turn:
$ py.test
collected 3 items
test_expectation.py ..F
================================= FAILURES =================================

____________________________ test_eval[6*9-42] _____________________________
input = '6*9', expected = 42
("3+5", 8),
("2+4", 6),
("6*9", 42),
])
> assert eval(input) == expected
E assert 54 == 42
E + where 54 = eval('6*9')
test_expectation.py:8: AssertionError
==================== 1 failed, 2 passed in 0.02 seconds ====================
As designed in this example, only one pair of input/output values fails the simple test function. And as usual with test
function arguments, you can see the input and output values in the traceback.
Note that you could also use the parametrize marker on a class or a module (see Marking test functions with attributes)
which would invoke several functions with the argument sets.

It is also possible to mark individual test instances within parametrize, for example with the builtin mark.xfail:
# content of test_expectation.py
import pytest
("3+5", 8),
("2+4", 6),
pytest.mark.xfail(("6*9", 42)),
])
assert eval(input) == expected
Let’s run this:

$ py.test
collected 3 items
test_expectation.py ..x
=================== 2 passed, 1 xfailed in 0.02 seconds ====================
The one parameter set which caused a failure previously now shows up as an “xfailed (expected to fail)” test.
Note: In versions prior to 2.4 one needed to specify the argument names as a tuple. This remains valid but the
simpler "name1,name2,..." comma-separated-string syntax is now advertised first because it’s easier to write
and produces less line noise.
2.6.2 Basic pytest_generate_tests example
Sometimes you may want to implement your own parametrization scheme or implement some dynamism for deter-
mining the parameters or scope of a fixture. For this, you can use the pytest_generate_tests hook which
is called when collecting a test function. Through the passed in metafunc object you can inspect the requesting test
context and, most importantly, you can call metafunc.parametrize() to cause parametrization.
For example, let’s say we want to run a test taking string inputs which we want to set via a new pytest command
line option. Let’s first write a simple test accepting a stringinput fixture function argument:
# content of test_strings.py
def test_valid_string(stringinput):
assert stringinput.isalpha()
Now we add a conftest.py file containing the addition of a command line option and the parametrization of our
test function:
def pytest_addoption(parser):
parser.addoption("--stringinput", action="append", default=[],
help="list of stringinputs to pass to test functions")
def pytest_generate_tests(metafunc):
if 'stringinput' in metafunc.fixturenames:
2.6. Parametrizing fixtures and test functions 49

metafunc.parametrize("stringinput",
metafunc.config.option.stringinput)
If we now pass two stringinput values, our test will run twice:
$ py.test -q --stringinput="hello" --stringinput="world" test_strings.py
..
Let’s also run with a stringinput that will lead to a failing test:
$ py.test -q --stringinput="!" test_strings.py
F
================================= FAILURES =================================
___________________________ test_valid_string[!] ___________________________
stringinput = '!'
def test_valid_string(stringinput):
> assert stringinput.isalpha()
E assert <built-in method isalpha of str object at 0x7f6e2145e768>()
E + where <built-in method isalpha of str object at 0x7f6e2145e768> = '!'.isalpha
test_strings.py:3: AssertionError
As expected our test function fails.

If you don’t specify a stringinput it will be skipped because metafunc.parametrize() will be called with an
empty parameter listlist:
$ py.test -q -rs test_strings.py
s
========================= short test summary info ==========================
SKIP [1] /tmp/sandbox/pytest/.tox/regen/lib/python3.4/site-packages/_pytest/python.py:1185: got empty
1 skipped in 0.01 seconds
For further examples, you might want to look at more parametrization examples.
2.6.3 The metafunc object
metafunc objects are passed to the pytest_generate_tests hook. They help to inspect a testfunction and to
generate tests according to test configuration or values specified in the class or module where a test function is defined:
metafunc.fixturenames: set of required function arguments for given function
metafunc.function: underlying python test function
metafunc.cls: class object where the test function is defined in or None.
metafunc.module: the module object where the test function is defined in.
metafunc.config: access to command line opts and general config
metafunc.funcargnames: alias for fixturenames, for pre-2.3 compatibility
Metafunc.parametrize(argnames, argvalues, indirect=False, ids=None, scope=None)
Add new invocations to the underlying test function using the list of argvalues for the given argnames.
Parametrization is performed during the collection phase. If you need to setup expensive resources see about
setting indirect=True to do it rather at test setup time.

Parameters
• argnames – a comma-separated string denoting one or more argument names, or a
list/tuple of argument strings.
• argvalues – The list of argvalues determines how often a test is invoked with different
argument values. If only one argname was specified argvalues is a list of simple values. If
N argnames were specified, argvalues must be a list of N-tuples, where each tuple-element
specifies a value for its respective argname.
• indirect – if True each argvalue corresponding to an argname will be passed as re-
quest.param to its respective argname fixture function so that it can perform more expensive
setups during the setup phase of a test rather than at collection time.
• ids – list of string ids, or a callable. If strings, each is corresponding to the argvalues so
that they are part of the test id. If callable, it should take one argument (a single argvalue)
and return a string or return None. If None, the automatically generated id for that argument
will be used. If no ids are provided they will be generated automatically from the argvalues.
• scope – if specified it denotes the scope of the parameters. The scope is used for group-
ing tests by parameter instances. It will also override any fixture-function defined scope,
allowing to set a dynamic scope using test context or configuration.
Metafunc.addcall(funcargs=None, id=_notexists, param=_notexists)
(deprecated, use parametrize) Add a new call to the underlying test function during the collection phase of a test
run. Note that request.addcall() is called during the test collection phase prior and independently to actual test
execution. You should only use addcall() if you need to specify multiple arguments of a test function.
Parameters
• funcargs – argument keyword dictionary used when invoking the test function.
• id – used for reporting and identification purposes. If you don’t supply an id an automatic
unique id will be generated.
• param – a parameter which will be exposed to a later fixture function invocation through
the request.param attribute.
2.7 classic xunit-style setup
This section describes a classic and popular way how you can implement fixtures (setup and teardown test state) on a
per-module/class/function basis. pytest started supporting these methods around 2005 and subsequently nose and the
standard library introduced them (under slightly different names). While these setup/teardown methods are and will
remain fully supported you may also use pytest’s more powerful fixture mechanism which leverages the concept of
dependency injection, allowing for a more modular and more scalable approach for managing test state, especially for
larger projects and for functional testing. You can mix both fixture mechanisms in the same file but unittest-based test
methods cannot receive fixture arguments.
Note: As of pytest-2.4, teardownX functions are not called if setupX existed and failed/was skipped. This harmonizes
behaviour across all major python testing tools.
2.7.1 Module level setup/teardown
If you have multiple test functions and test classes in a single module you can optionally implement the following
fixture methods which will usually be called once for all the functions:
2.7. classic xunit-style setup 51

def setup_module(module):
""" setup any state specific to the execution of the given module."""
def teardown_module(module):
""" teardown any state that was previously setup with a setup_module
method.
"""
2.7.2 Class level setup/teardown
Similarly, the following methods are called at class level before and after all test methods of the class are called:
@classmethod
def setup_class(cls):
""" setup any state specific to the execution of the given class (which
usually contains tests).
"""
@classmethod
def teardown_class(cls):
""" teardown any state that was previously setup with a call to
setup_class.
"""
2.7.3 Method and function level setup/teardown
Similarly, the following methods are called around each method invocation:
def setup_method(self, method):
""" setup any state tied to the execution of the given method in a
class. setup_method is invoked for every test method of a class.
"""
def teardown_method(self, method):

""" teardown any state that was previously setup with a setup_method
call.
"""
If you would rather define test functions directly at module level you can also use the following functions to implement
fixtures:
def setup_function(function):
""" setup any state tied to the execution of the given function.
Invoked for every test function in the module.
"""
def teardown_function(function):
""" teardown any state that was previously setup with a setup_function
call.
"""
Note that it is possible for setup/teardown pairs to be invoked multiple times per testing process.

2.8 Capturing of the stdout/stderr output
2.8.1 Default stdout/stderr/stdin capturing behaviour
During test execution any output sent to stdout and stderr is captured. If a test or a setup method fails its
according captured output will usually be shown along with the failure traceback.
In addition, stdin is set to a “null” object which will fail on attempts to read from it because it is rarely desired to
wait for interactive input when running automated tests.
By default capturing is done by intercepting writes to low level file descriptors. This allows to capture output from
simple print statements as well as output from a subprocess started by a test.
2.8.2 Setting capturing methods or disabling capturing
There are two ways in which pytest can perform capturing:

• file descriptor (FD) level capturing (default): All writes going to the operating system file descriptors 1 and 2
will be captured.
• sys level capturing: Only writes to Python files sys.stdout and sys.stderr will be captured. No
capturing of writes to filedescriptors is performed.
You can influence output capturing mechanisms from the command line:
py.test -s # disable all capturing
py.test --capture=sys # replace sys.stdout/stderr with in-mem files
py.test --capture=fd # also point filedescriptors 1 and 2 to temp file
2.8.3 Using print statements for debugging
One primary benefit of the default capturing of stdout/stderr output is that you can use print statements for debugging:
def setup_function(function):
print ("setting up %s" % function)
def test_func1():
assert True
def test_func2():
assert False
and running this module will show you precisely the output of the failing function and hide the other one:
$ py.test
collected 2 items
test_module.py .F
================================= FAILURES =================================

________________________________ test_func2 ________________________________
2.8. Capturing of the stdout/stderr output 53

def test_func2():
> assert False
E assert False
-------------------------- Captured stdout setup ---------------------------
setting up <function test_func2 at 0x7fa678d6eb70>
2.8.4 Accessing captured output from a test function
The capsys and capfd fixtures allow to access stdout/stderr output created during test execution. Here is an example
test function that performs some output related checks:
def test_myoutput(capsys): # or use "capfd" for fd-level
print ("hello")
sys.stderr.write("world\n")
out, err = capsys.readouterr()
assert out == "hello\n"
assert err == "world\n"
print "next"
out, err = capsys.readouterr()
assert out == "next\n"
The readouterr() call snapshots the output so far - and capturing will be continued. After the test function finishes
the original streams will be restored. Using capsys this way frees your test from having to care about setting/resetting
output streams and also interacts well with pytest’s own per-test capturing.
If you want to capture on filedescriptor level you can use the capfd function argument which offers the exact same
interface but allows to also capture output from libraries or subprocesses that directly write to operating system level
output streams (FD1 and FD2).
2.9 Monkeypatching/mocking modules and environments
Sometimes tests need to invoke functionality which depends on global settings or which invokes code which cannot
be easily tested such as network access. The monkeypatch function argument helps you to safely set/delete an
attribute, dictionary item or environment variable or to modify sys.path for importing. See the monkeypatch blog
post for some introduction material and a discussion of its motivation.
2.9.1 Simple example: monkeypatching functions
If you want to pretend that os.expanduser returns a certain directory, you can use the
monkeypatch.setattr() method to patch this function before calling into a function which uses it:
import os.path
def getssh(): # pseudo application code
return os.path.join(os.path.expanduser("~admin"), '.ssh')
def test_mytest(monkeypatch):
def mockreturn(path):
return '/abc'
monkeypatch.setattr(os.path, 'expanduser', mockreturn)

x = getssh()
assert x == '/abc/.ssh'
Here our test function monkeypatches os.path.expanduser and then calls into an function that calls it. After the
test function finishes the os.path.expanduser modification will be undone.
2.9.2 example: preventing “requests” from remote operations
If you want to prevent the “requests” library from performing http requests in all your tests, you can do:
import pytest
def no_requests(monkeypatch):
monkeypatch.delattr("requests.sessions.Session.request")
This autouse fixture will be executed for each test function and it will delete the method
request.session.Session.request so that any attempts within tests to create http requests will fail.
2.9.3 example: setting an attribute on some class
If you need to patch out os.getcwd() to return an artificial value:

def test_some_interaction(monkeypatch):
monkeypatch.setattr("os.getcwd", lambda: "/")
which is equivalent to the long form:

def test_some_interaction(monkeypatch):
import os
monkeypatch.setattr(os, "getcwd", lambda: "/")
2.9.4 Method reference of the monkeypatch function argument
class monkeypatch
Object keeping a record of setattr/item/env/syspath changes.
setattr(target, name, value=<notset>, raising=True)
Set attribute value on target, memorizing the old value. By default raise AttributeError if the attribute did
not exist.
For convenience you can specify a string as target which will be interpreted as a dotted import path,
with the last part being the attribute name. Example: monkeypatch.setattr("os.getcwd",
lambda x: "/") would set the getcwd function of the os module.
The raising value determines if the setattr should fail if the attribute is not already present (defaults to
True which means it will raise).
delattr(target, name=<notset>, raising=True)
Delete attribute name from target, by default raise AttributeError it the attribute did not previously
exist.
If no name is specified and target is a string it will be interpreted as a dotted import path with the last
part being the attribute name.
If raising is set to False, no exception will be raised if the attribute is missing.
2.9. Monkeypatching/mocking modules and environments 55

setitem(dic, name, value)

Set dictionary entry name to value.
delitem(dic, name, raising=True)
Delete name from dict. Raise KeyError if it doesn’t exist.
If raising is set to False, no exception will be raised if the key is missing.
setenv(name, value, prepend=None)
Set environment variable name to value. If prepend is a character, read the current environment
variable value and prepend the value adjoined with the prepend character.
delenv(name, raising=True)
Delete name from the environment. Raise KeyError it does not exist.
If raising is set to False, no exception will be raised if the environment variable is missing.
syspath_prepend(path)
Prepend path to sys.path list of import locations.
chdir(path)
Change the current working directory to the specified path path can be a string or a py.path.local object
undo()
Undo previous changes. This call consumes the undo stack. Calling it a second time has no effect unless
you do more monkeypatching after the undo call.
monkeypatch.setattr/delattr/delitem/delenv() all by default raise an Exception if the target does
not exist. Pass raising=False if you want to skip this check.
2.10 xdist: pytest distributed testing plugin
The pytest-xdist plugin extends pytest with some unique test execution modes:
• Looponfail: run your tests repeatedly in a subprocess. After each run, pytest waits until a file in your project
changes and then re-runs the previously failing tests. This is repeated until all tests pass. At this point a full run
is again performed.
• multiprocess Load-balancing: if you have multiple CPUs or hosts you can use them for a combined test run.
This allows to speed up development or to use special resources of remote machines.
• Multi-Platform coverage: you can specify different Python interpreters or different platforms and run tests in
parallel on all of them.
Before running tests remotely, pytest efficiently “rsyncs” your program source code to the remote place. All test
results are reported back and displayed to your local terminal. You may specify different Python versions and inter-
preters.
2.10.1 Installation of xdist plugin
Install the plugin with:

easy_install pytest-xdist
# or
pip install pytest-xdist

or use the package in develop/in-place mode with a checkout of the pytest-xdist repository
python setup.py develop
2.10.2 Usage examples
Speed up test runs by sending tests to multiple CPUs
To send tests to multiple CPUs, type:

py.test -n NUM
Especially for longer running tests or tests requiring a lot of I/O this can lead to considerable speed ups.
Running tests in a Python subprocess
To instantiate a Python-2.4 subprocess and send tests to it, you may type:
py.test -d --tx popen//python=python2.4
This will start a subprocess which is run with the “python2.4” Python interpreter, found in your system binary lookup
path.
If you prefix the –tx option value like this:
py.test -d --tx 3*popen//python=python2.4
then three subprocesses would be created and the tests will be distributed to three subprocesses and run simultanously.
Running tests in looponfailing mode
For refactoring a project with a medium or large test suite you can use the looponfailing mode. Simply add the --f
option:
py.test -f
and pytest will run your tests. Assuming you have failures it will then wait for file changes and re-run the failing
test set. File changes are detected by looking at looponfailingroots root directories and all of their contents
(recursively). If the default for this value does not work for you you can change it in your project by setting a
configuration option:
# content of a pytest.ini, setup.cfg or tox.ini file
[pytest]
looponfailroots = mypkg testdir
This would lead to only looking for file changes in the respective directories, specified relatively to the ini-file’s
directory.
Sending tests to remote SSH accounts
Suppose you have a package mypkg which contains some tests that you can successfully run locally. And you also
have a ssh-reachable machine myhost. Then you can ad-hoc distribute your tests by typing:
py.test -d --tx ssh=myhostpopen --rsyncdir mypkg mypkg
2.10. xdist: pytest distributed testing plugin 57

This will synchronize your mypkg package directory with a remote ssh account and then collect and run your tests at
the remote side.
You can specify multiple --rsyncdir directories to be sent to the remote side.
Sending tests to remote Socket Servers
Download the single-module socketserver.py Python program and run it like this:
python socketserver.py
It will tell you that it starts listening on the default port. You can now on your home machine specify this new socket
host with something like this:
py.test -d --tx socket=192.168.1.102:8888 --rsyncdir mypkg mypkg
Running tests on many platforms at once
The basic command to run tests on multiple platforms is:

py.test --dist=each --tx=spec1 --tx=spec2
If you specify a windows host, an OSX host and a Linux environment this command will send each tests to all platforms
- and report back failures from all platforms at once. The specifications strings use the xspec syntax.
Specifying test exec environments in an ini file
pytest (since version 2.0) supports ini-style configuration. For example, you could make running with three subpro-
cesses your default:
[pytest]
addopts = -n3
You can also add default environments like this:

[pytest]
addopts = --tx ssh=myhost//python=python2.5 --tx ssh=myhost//python=python2.6
and then just type:

py.test --dist=each
to run tests in each of the environments.
Specifying “rsync” dirs in an ini-file
In a tox.ini or setup.cfg file in your root project directory you may specify directories to include or to exclude
in synchronisation:
[pytest]
rsyncdirs = . mypkg helperpkg
rsyncignore = .hg
These directory specifications are relative to the directory where the configuration file was found.

2.11 Temporary directories and files
2.11.1 The ‘tmpdir’ test function argument
You can use the tmpdir function argument which will provide a temporary directory unique to the test invocation,
created in the base temporary directory.
tmpdir is a py.path.local object which offers os.path methods and more. Here is an example test usage:
# content of test_tmpdir.py
import os
def test_create_file(tmpdir):
p = tmpdir.mkdir("sub").join("hello.txt")
p.write("content")
assert p.read() == "content"
assert len(tmpdir.listdir()) == 1
assert 0
Running this would result in a passed test except for the last assert 0 line which we use to look at values:
$ py.test test_tmpdir.py
collected 1 items
test_tmpdir.py F
================================= FAILURES =================================

_____________________________ test_create_file _____________________________
tmpdir = local('/tmp/pytest-19/test_create_file0')
def test_create_file(tmpdir):
p = tmpdir.mkdir("sub").join("hello.txt")
p.write("content")
assert p.read() == "content"
assert len(tmpdir.listdir()) == 1
> assert 0
E assert 0
test_tmpdir.py:7: AssertionError
2.11.2 The default base temporary directory
Temporary directories are by default created as sub-directories of the system temporary directory. The base name
will be pytest-NUM where NUM will be incremented with each test run. Moreover, entries older than 3 temporary
directories will be removed.
You can override the default temporary directory setting like this:
py.test --basetemp=mydir
When distributing tests on the local machine, pytest takes care to configure a basetemp directory for the sub pro-
cesses such that all temporary data lands below a single per-test run basetemp directory.
2.11. Temporary directories and files 59

2.12 Marking test functions with attributes
By using the pytest.mark helper you can easily set metadata on your test functions. There are some builtin
markers, for example:
• skipif - skip a test function if a certain condition is met
• xfail - produce an “expected failure” outcome if a certain condition is met
• parametrize to perform multiple calls to the same test function.
It’s easy to create custom markers or to apply markers to whole test classes or modules. See Working with custom
markers for examples which also serve as documentation.
2.12.1 API reference for mark related objects
class MarkGenerator
Factory for MarkDecorator objects - exposed as a pytest.mark singleton instance. Example:
import py
@pytest.mark.slowtest
pass
will set a ‘slowtest’ MarkInfo object on the test_function object.

class MarkDecorator(name, args=None, kwargs=None)
A decorator for test functions and test classes. When applied it will create MarkInfo objects which may be
retrieved by hooks as item keywords. MarkDecorator instances are often created like this:
mark1 = pytest.mark.NAME # simple MarkDecorator
mark2 = pytest.mark.NAME(name1=value) # parametrized MarkDecorator
and can then be applied as decorators to test functions:

@mark2
pass
When a MarkDecorator instance is called it does the following:

1. If called with a single class as its only positional argument and no additional keyword arguments, it
attaches itself to the class so it gets applied automatically to all test cases found in that class.
2. If called with a single function as its only positional argument and no additional keyword arguments,
it attaches a MarkInfo object to the function, containing all the arguments already stored internally in
the MarkDecorator.
3. When called in any other case, it performs a ‘fake construction’ call, i.e. it returns a new MarkDec-
orator instance with the original MarkDecorator’s content updated with the arguments passed to this
call.
Note: The rules above prevent MarkDecorator objects from storing only a single function or class reference as
their positional argument with no additional keyword or positional arguments.
class MarkInfo(name, args, kwargs)
Marking object created by MarkDecorator instances.

name = None
name of attribute
args = None
positional argument list, empty if none specified
kwargs = None
keyword argument dictionary, empty if nothing specified
add(args, kwargs)
add a MarkInfo with the given args and kwargs.
2.13 Skip and xfail: dealing with tests that can not succeed
If you have test functions that cannot be run on certain platforms or that you expect to fail you can mark them
accordingly or you may call helper functions during execution of setup or test functions.
A skip means that you expect your test to pass unless the environment (e.g. wrong Python interpreter, missing de-
pendency) prevents it to run. And xfail means that your test can run but you expect it to fail because there is an
implementation problem.
pytest counts and lists skip and xfail tests separately. Detailed information about skipped/xfailed tests is not shown
by default to avoid cluttering the output. You can use the -r option to see details corresponding to the “short” letters
shown in the test progress:
py.test -rxs # show extra info on skips and xfails
(See How to change command line options defaults)
2.13.1 Marking a test function to be skipped
New in version 2.0,: 2.4

Here is an example of marking a test function to be skipped when run on a Python3.3 interpreter:
import sys
@pytest.mark.skipif(sys.version_info < (3,3),
reason="requires python3.3")
...
During test function setup the condition (“sys.version_info >= (3,3)”) is checked. If it evaluates to True, the test
function will be skipped with the specified reason. Note that pytest enforces specifying a reason in order to report
meaningful “skip reasons” (e.g. when using -rs). If the condition is a string, it will be evaluated as python expression.
You can share skipif markers between modules. Consider this test module:
# content of test_mymodule.py
import mymodule
minversion = pytest.mark.skipif(mymodule.__versioninfo__ < (1,1),
reason="at least mymodule-1.1 required")
@minversion
...
You can import it from another test module:
2.13. Skip and xfail: dealing with tests that can not succeed 61
# test_myothermodule.py
from test_mymodule import minversion
@minversion
def test_anotherfunction():
...
For larger test suites it’s usually a good idea to have one file where you define the markers which you then consistently
apply throughout your test suite.
Alternatively, the pre pytest-2.4 way to specify condition strings instead of booleans will remain fully supported in
future versions of pytest. It couldn’t be easily used for importing markers between test modules so it’s no longer
advertised as the primary method.
2.13.2 Skip all test functions of a class or module
As with all function marking you can skip test functions at the whole class- or module level. If your code targets
python2.6 or above you use the skipif decorator (and any other marker) on classes:
@pytest.mark.skipif(sys.platform == 'win32',
reason="requires windows")
class TestPosixCalls:
def test_function(self):
"will not be setup or run under 'win32' platform"
If the condition is true, this marker will produce a skip result for each of the test methods.
If your code targets python2.5 where class-decorators are not available, you can set the pytestmark attribute of a
class:
class TestPosixCalls:
pytestmark = pytest.mark.skipif(sys.platform == 'win32',
reason="requires Windows")
def test_function(self):
"will not be setup or run under 'win32' platform"
As with the class-decorator, the pytestmark special name tells pytest to apply it to each test function in the class.
If you want to skip all test functions of a module, you must use the pytestmark name on the global level:
# test_module.py
pytestmark = pytest.mark.skipif(...)
If multiple “skipif” decorators are applied to a test function, it will be skipped if any of the skip conditions is true.
2.13.3 Mark a test function as expected to fail
You can use the xfail marker to indicate that you expect the test to fail:
@pytest.mark.xfail
...
This test will be run but no traceback will be reported when it fails. Instead terminal reporting will list it in the
“expected to fail” or “unexpectedly passing” sections.

By specifying on the commandline:

pytest --runxfail
you can force the running and reporting of an xfail marked test as if it weren’t marked at all.
As with skipif you can also mark your expectation of a failure on a particular platform:
@pytest.mark.xfail(sys.version_info >= (3,3),
reason="python3.3 api changes")
...
If you want to be more specific as to why the test is failing, you can specify a single exception, or a list of exceptions,
in the raises argument. Then the test will be reported as a regular failure if it fails with an exception not mentioned
in raises.
You can furthermore prevent the running of an “xfail” test or specify a reason such as a bug ID or similar. Here is a
simple test file with the several usages:
import pytest
xfail = pytest.mark.xfail
@xfail
def test_hello():
assert 0
@xfail(run=False)
def test_hello2():
assert 0
@xfail("hasattr(os, 'sep')")
def test_hello3():
assert 0
@xfail(reason="bug 110")
def test_hello4():
assert 0
@xfail('pytest.__version__[0] != "17"')
def test_hello5():
assert 0
def test_hello6():
pytest.xfail("reason")
@xfail(raises=IndexError)
def test_hello7():
x = []
x[1] = 1
Running it with the report-on-xfail option gives this output:

example $ py.test -rx xfail_demo.py
rootdir: /tmp/sandbox/pytest/doc/en, inifile: pytest.ini
collected 7 items
xfail_demo.py xxxxxxx

XFAIL xfail_demo.py::test_hello
XFAIL xfail_demo.py::test_hello2
reason: [NOTRUN]
condition: hasattr(os, 'sep')
bug 110
condition: pytest.__version__[0] != "17"
reason: reason
======================== 7 xfailed in 0.06 seconds =========================
2.13.4 Skip/xfail with parametrize
It is possible to apply markers like skip and xfail to individual test instances when using parametrize:
import pytest
@pytest.mark.parametrize(("n", "expected"), [
(1, 2),
pytest.mark.xfail((1, 0)),
pytest.mark.xfail(reason="some bug")((1, 3)),
(2, 3),
(3, 4),
(4, 5),
pytest.mark.skipif("sys.version_info >= (3,0)")((10, 11)),
])
def test_increment(n, expected):
assert n + 1 == expected
2.13.5 Imperative xfail from within a test or setup function
If you cannot declare xfail- of skipif conditions at import time you can also imperatively produce an according outcome
imperatively, in test or setup code:
if not valid_config():
pytest.xfail("failing configuration (but should work)")
# or
pytest.skip("unsupported configuration")
2.13.6 Skipping on a missing import dependency
You can use the following import helper at module level or within a test or test setup function:
docutils = pytest.importorskip("docutils")
If docutils cannot be imported here, this will lead to a skip outcome of the test. You can also skip based on the
version number of a library:

docutils = pytest.importorskip("docutils", minversion="0.3")
The version will be read from the specified module’s __version__ attribute.
2.13.7 specifying conditions as strings versus booleans
Prior to pytest-2.4 the only way to specify skipif/xfail conditions was to use strings:
import sys
@pytest.mark.skipif("sys.version_info >= (3,3)")
...
During test function setup the skipif condition is evaluated by calling eval(’sys.version_info >=
(3,0)’, namespace). The namespace contains all the module globals, and os and sys as a minimum.
Since pytest-2.4 condition booleans are considered preferable because markers can then be freely imported between
test modules. With strings you need to import not only the marker but all variables everything used by the marker,
which violates encapsulation.
The reason for specifying the condition as a string was that pytest can report a summary of skip conditions based
purely on the condition string. With conditions as booleans you are required to specify a reason string.
Note that string conditions will remain fully supported and you are free to use them if you have no need for cross-
importing markers.
The evaluation of a condition string in pytest.mark.skipif(conditionstring) or
pytest.mark.xfail(conditionstring) takes place in a namespace dictionary which is constructed
as follows:
• the namespace is initialized by putting the sys and os modules and the pytest config object into it.
• updated with the module globals of the test function for which the expression is applied.
The pytest config object allows you to skip based on a test configuration value which you might have added:
@pytest.mark.skipif("not config.getvalue('db')")
def test_function(...):
...
The equivalent with “boolean conditions” is:

@pytest.mark.skipif(not pytest.config.getvalue("db"),
reason="--db was not specified")
def test_function(...):
pass
Note: You cannot use pytest.config.getvalue() in code imported before py.test’s argument pars-
ing takes place. For example, conftest.py files are imported before command line parsing and thus
config.getvalue() will not execute correctly.
2.14 Asserting deprecation and other warnings
2.14.1 The recwarn function argument
You can use the recwarn funcarg to assert that code triggers warnings through the Python warnings system. Here is
a simple self-contained test:
# content of test_recwarn.py
def test_hello(recwarn):
from warnings import warn
warn("hello", DeprecationWarning)
w = recwarn.pop(DeprecationWarning)
assert issubclass(w.category, DeprecationWarning)
assert 'hello' in str(w.message)
assert w.filename
assert w.lineno
The recwarn function argument provides these methods:

• pop(category=None): return last warning matching the category.
• clear(): clear list of warnings
2.14.2 Ensuring a function triggers a deprecation warning
You can also call a global helper for checking that a certain function call triggers a Deprecation warning:
import pytest
def test_global():
pytest.deprecated_call(myfunction, 17)
2.15 Support for unittest.TestCase / Integration of fixtures
pytest has support for running Python unittest.py style tests. It’s meant for leveraging existing unittest-style
projects to use pytest features. Concretely, pytest will automatically collect unittest.TestCase subclasses
and their test methods in test files. It will invoke typical setup/teardown methods and generally try to make test
suites written to run on unittest, to also run using pytest. We assume here that you are familiar with writing
unittest.TestCase style tests and rather focus on integration aspects.
2.15.1 Usage
After Installation type:

py.test
and you should be able to run your unittest-style tests if they are contained in test_* modules. If that works for
you then you can make use of most pytest features, for example --pdb debugging in failures, using plain assert-
statements, more informative tracebacks, stdout-capturing or distributing tests to multiple CPUs via the -nNUM option
if you installed the pytest-xdist plugin. Please refer to the general pytest documentation for many more
examples.

2.15.2 Mixing pytest fixtures into unittest.TestCase style tests
Running your unittest with pytest allows you to use its fixture mechanism with unittest.TestCase style tests.
Assuming you have at least skimmed the pytest fixture features, let’s jump-start into an example that integrates a pytest
db_class fixture, setting up a class-cached database object, and then reference it from a unittest-style test:
# we define a fixture function below and it will be "used" by

# referencing its name from tests
import pytest
@pytest.fixture(scope="class")
def db_class(request):
class DummyDB:
pass
# set a class attribute on the invoking test context
request.cls.db = DummyDB()
This defines a fixture function db_class which - if used - is called once for each test class and which sets the class-
level db attribute to a DummyDB instance. The fixture function achieves this by receiving a special request object
which gives access to the requesting test context such as the cls attribute, denoting the class from which the fixture is
used. This architecture de-couples fixture writing from actual test code and allows re-use of the fixture by a minimal
reference, the fixture name. So let’s write an actual unittest.TestCase class using our fixture definition:
# content of test_unittest_db.py
import unittest
import pytest
@pytest.mark.usefixtures("db_class")
class MyTest(unittest.TestCase):
assert hasattr(self, "db")
assert 0, self.db # fail for demo purposes
assert 0, self.db # fail for demo purposes
The @pytest.mark.usefixtures("db_class") class-decorator makes sure that the pytest fixture function
db_class is called once per class. Due to the deliberately failing assert statements, we can take a look at the
self.db values in the traceback:
$ py.test test_unittest_db.py
collected 2 items
test_unittest_db.py FF
================================= FAILURES =================================

___________________________ MyTest.test_method1 ____________________________
self = <test_unittest_db.MyTest testMethod=test_method1>
assert hasattr(self, "db")
2.15. Support for unittest.TestCase / Integration of fixtures 67

> assert 0, self.db # fail for demo purposes

E AssertionError: <conftest.db_class.<locals>.DummyDB object at 0x7f97382031d0>
E assert 0
test_unittest_db.py:9: AssertionError
___________________________ MyTest.test_method2 ____________________________
self = <test_unittest_db.MyTest testMethod=test_method2>
> assert 0, self.db # fail for demo purposes
E AssertionError: <conftest.db_class.<locals>.DummyDB object at 0x7f97382031d0>
E assert 0
test_unittest_db.py:12: AssertionError
This default pytest traceback shows that the two test methods share the same self.db instance which was our
intention when writing the class-scoped fixture function above.
2.15.3 autouse fixtures and accessing other fixtures
Although it’s usually better to explicitely declare use of fixtures you need for a given test, you may sometimes want to
have fixtures that are automatically used in a given context. After all, the traditional style of unittest-setup mandates
the use of this implicit fixture writing and chances are, you are used to it or like it.
You can flag fixture functions with @pytest.fixture(autouse=True) and define the fixture function in the
context where you want it used. Let’s look at an initdir fixture which makes all test methods of a TestCase
class execute in a temporary directory with a pre-initialized samplefile.ini. Our initdir fixture itself uses
the pytest builtin tmpdir fixture to delegate the creation of a per-test temporary directory:
# content of test_unittest_cleandir.py
import pytest
import unittest
class MyTest(unittest.TestCase):
def initdir(self, tmpdir):
tmpdir.chdir() # change to pytest-provided temporary directory
tmpdir.join("samplefile.ini").write("# testdata")
def test_method(self):
s = open("samplefile.ini").read()
assert "testdata" in s
Due to the autouse flag the initdir fixture function will be used for all methods of the class where it is de-
fined. This is a shortcut for using a @pytest.mark.usefixtures("initdir") marker on the class like in
the previous example.
Running this test module ...:
$ py.test -q test_unittest_cleandir.py
.
... gives us one passed test because the initdir fixture function was executed ahead of the test_method.
Note: While pytest supports receiving fixtures via test function arguments for non-unittest test methods,

unittest.TestCase methods cannot directly receive fixture function arguments as implementing that is likely to
inflict on the ability to run general unittest.TestCase test suites. Maybe optional support would be possible, though.
If unittest finally grows a plugin system that should help as well. In the meanwhile, the above usefixtures and
autouse examples should help to mix in pytest fixtures into unittest suites. And of course you can also start to
selectively leave away the unittest.TestCase subclassing, use plain asserts and get the unlimited pytest feature
set.
2.16 Running tests written for nose
pytest has basic support for running tests written for nose.
2.16.1 Usage
After Installation type:

python setup.py develop # make sure tests can import our package
py.test # instead of 'nosetests'
and you should be able to run your nose style tests and make use of pytest’s capabilities.
2.16.2 Supported nose Idioms
• setup and teardown at module/class/method level

• SkipTest exceptions and markers
• setup/teardown decorators
• yield-based tests and their setup
• __test__ attribute on modules/classes/functions
• general usage of nose utilities
2.16.3 Unsupported idioms / known issues
• unittest-style setUp, tearDown, setUpClass, tearDownClass are recognized only on

unittest.TestCase classes but not on plain classes. nose supports these methods also on plain
classes but pytest deliberately does not. As nose and pytest already both support setup_class,
teardown_class, setup_method, teardown_method it doesn’t seem useful to duplicate the
unittest-API like nose does. If you however rather think pytest should support the unittest-spelling on plain
classes please post to this issue.
• nose imports test modules with the same import path (e.g. tests.test_mod) but different file system paths
(e.g. tests/test_mode.py and other/tests/test_mode.py) by extending sys.path/import seman-
tics. pytest does not do that but there is discussion in issue268 for adding some support. Note that nose2 choose
to avoid this sys.path/import hackery.
• nose-style doctests are not collected and executed correctly, also doctest fixtures don’t work.
• no nose-configuration is recognized
2.16. Running tests written for nose 69

2.17 Doctest integration for modules and test files
By default all files matching the test*.txt pattern will be run through the python standard doctest module. You
can change the pattern by issuing:
py.test --doctest-glob='*.rst'
on the command line. You can also trigger running of doctests from docstrings in all python modules (including
regular python test modules):
py.test --doctest-modules
You can make these changes permanent in your project by putting them into a pytest.ini file like this:
[pytest]
addopts = --doctest-modules
If you then have a text file like this:

# content of example.rst
hello this is a doctest

>>> x = 3
>>> x
3
and another like this:

# content of mymodule.py
def something():
""" a doctest in a docstring
>>> something()
42
"""
return 42
then you can just invoke py.test without command line options:
$ py.test
rootdir: /tmp/doc-exec-96, inifile: pytest.ini
collected 1 items
mymodule.py .
It is possible to use fixtures using the getfixture helper:

# content of example.rst
>>> tmp = getfixture('tmpdir')
>>> ...
>>>
Also, using fixtures from classes, modules or projects and autouse fixtures (xUnit setup on steroids) fixtures are sup-
ported when executing text doctest files.

The standard doctest module provides some setting flags to configure the strictness of doctest tests. In py.test You
can enable those flags those flags using the configuration file. To make pytest ignore trailing whitespaces and ignore
lengthy exception stack traces you can just write:
[pytest]
doctest_optionflags= NORMALIZE_WHITESPACE IGNORE_EXCEPTION_DETAIL
2.17. Doctest integration for modules and test files 71


CHAPTER
THREE
WORKING WITH PLUGINS AND CONFTEST FILES
pytest implements all aspects of configuration, collection, running and reporting by calling well specified hooks.
Virtually any Python module can be registered as a plugin. It can implement any number of hook functions (usually
two or three) which all have a pytest_ prefix, making hook functions easy to distinguish and find. There are three
basic location types:
• builtin plugins: loaded from pytest’s internal _pytest directory.
• external plugins: modules discovered through setuptools entry points
• conftest.py plugins: modules auto-discovered in test directories
3.1 conftest.py: local per-directory plugins
local conftest.py plugins contain directory-specific hook implementations. Session and test running activities
will invoke all hooks defined in conftest.py files closer to the root of the filesystem. Example: Assume the
following layout and content of files:
a/conftest.py:
def pytest_runtest_setup(item):
# called for running each test in 'a' directory
print ("setting up", item)
a/test_sub.py:
def test_sub():
pass
test_flat.py:
def test_flat():
pass
Here is how you might run it:

py.test test_flat.py # will not show "setting up"
py.test a/test_sub.py # will show "setting up"
Note: If you have conftest.py files which do not reside in a python package directory (i.e. one containing an
__init__.py) then “import conftest” can be ambiguous because there might be other conftest.py files as well
on your PYTHONPATH or sys.path. It is thus good practise for projects to either put conftest.py under a
package scope or to never import anything from a conftest.py file.
73
3.2 Installing External Plugins / Searching
Installing a plugin happens through any usual Python installation tool, for example:
pip install pytest-NAME
pip uninstall pytest-NAME
If a plugin is installed, pytest automatically finds and integrates it, there is no need to activate it. We have a page
listing all 3rd party plugins and their status against the latest py.test version and here is a little annotated list for some
popular plugins:
• pytest-django: write tests for django apps, using pytest integration.
• pytest-twisted: write tests for twisted apps, starting a reactor and processing deferreds from test functions.
• pytest-capturelog: to capture and assert about messages from the logging module
• pytest-cov: coverage reporting, compatible with distributed testing
• pytest-xdist: to distribute tests to CPUs and remote hosts, to run in boxed mode which allows to survive seg-
mentation faults, to run in looponfailing mode, automatically re-running failing tests on file changes, see also
xdist: pytest distributed testing plugin
• pytest-instafail: to report failures while the test run is happening.
• pytest-bdd and pytest-konira to write tests using behaviour-driven testing.
• pytest-timeout: to timeout tests based on function marks or global definitions.
• pytest-cache: to interactively re-run failing tests and help other plugins to store test run information across
invocations.
• pytest-pep8: a --pep8 option to enable PEP8 compliance checking.
• oejskit: a plugin to run javascript unittests in life browsers
To see a complete list of all plugins with their latest testing status against different py.test and Python versions, please
visit plugincompat.
You may also discover more plugins through a pytest- pypi.python.org search.
3.3 Writing a plugin by looking at examples
If you want to write a plugin, there are many real-life examples you can copy from:
• a custom collection example plugin: A basic example for specifying tests in Yaml files
• around 20 builtin plugins which provide pytest’s own functionality
• many external plugins providing additional features
All of these plugins implement the documented well specified hooks to extend and add functionality.
You can also contribute your plugin to pytest-dev once it has some happy users other than yourself.
3.4 Making your plugin installable by others
If you want to make your plugin externally available, you may define a so-called entry point for your distribution so
that pytest finds your plugin module. Entry points are a feature that is provided by setuptools. pytest looks up
74 Chapter 3. Working with plugins and conftest files

the pytest11 entrypoint to discover its plugins and you can thus make your plugin available by defining it in your
setuptools-invocation:
# sample ./setup.py file
from setuptools import setup
setup(
name="myproject",
packages = ['myproject']
# the following makes a plugin available to pytest

entry_points = {
'pytest11': [
'name_of_plugin = myproject.pluginmodule',
]
},
)
If a package is installed this way, pytest will load myproject.pluginmodule as a plugin which can define
well specified hooks.
3.5 Plugin discovery order at tool startup
pytest loads plugin modules at tool startup in the following way:

• by loading all builtin plugins
• by loading all plugins registered through setuptools entry points.
• by pre-scanning the command line for the -p name option and loading the specified plugin before actual
command line parsing.
• by loading all conftest.py files as inferred by the command line invocation:
– if no test paths are specified use current dir as a test path
– if exists, load conftest.py and test*/conftest.py relative to the directory part of the first test
path.
Note that pytest does not find conftest.py files in deeper nested sub directories at tool startup. It is usually
a good idea to keep your conftest.py file in the top level test or project root directory.
• by recursively loading all plugins specified by the pytest_plugins variable in conftest.py files
3.6 Requiring/Loading plugins in a test module or conftest file
You can require plugins in a test module or a conftest file like this:
pytest_plugins = "name1", "name2",
When the test module or conftest plugin is loaded the specified plugins will be loaded as well. You can also use dotted
path like this:
pytest_plugins = "myapp.testsupport.myplugin"
which will import the specified module as a pytest plugin.
3.5. Plugin discovery order at tool startup 75

3.7 Accessing another plugin by name
If a plugin wants to collaborate with code from another plugin it can obtain a reference through the plugin manager
like this:
plugin = config.pluginmanager.getplugin("name_of_plugin")
If you want to look at the names of existing plugins, use the --traceconfig option.
3.8 Finding out which plugins are active
If you want to find out which plugins are active in your environment you can type:
py.test --traceconfig
and will get an extended test header which shows activated plugins and their names. It will also print local plugins aka
conftest.py files when they are loaded.
3.9 Deactivating / unregistering a plugin by name
You can prevent plugins from loading or unregister them:

py.test -p no:NAME
This means that any subsequent try to activate/load the named plugin will it already existing. See Finding out which
plugins are active for how to obtain the name of a plugin.
76 Chapter 3. Working with plugins and conftest files

CHAPTER
FOUR
PYTEST DEFAULT PLUGIN REFERENCE
You can find the source code for the following plugins in the pytest repository.
_pytest.assertion support for presenting detailed information in failing assertions.

_pytest.capture per-test stdout/stderr capturing mechanism.
_pytest.config command line options, ini-file and conftest.py processing.
_pytest.doctest discover and run doctests in modules and test files.
_pytest.genscript generate a single-file self-contained version of pytest
_pytest.helpconfig version info, help messages, tracing configuration.
_pytest.junitxml report test results in JUnit-XML format, for use with Hudson and build integration servers.
_pytest.mark generic mechanism for marking and selecting python functions.
_pytest.monkeypatch monkeypatching and mocking functionality.
_pytest.nose run test suites written for nose.
_pytest.pastebin submit failure or test session information to a pastebin service.
_pytest.pdb interactive debugging with PDB, the Python Debugger.
_pytest.pytester (disabled by default) support for testing pytest and pytest plugins.
_pytest.python Python test discovery, setup and run of test functions.
_pytest.recwarn recording warnings during test function execution.
_pytest.resultlog log machine-parseable test session result information in a plain
_pytest.runner basic collect and runtest protocol implementations
_pytest.main core implementation of testing process: init, session, runtest loop.
_pytest.skipping support for skip/xfail functions and markers.
_pytest.terminal terminal reporting of the full testing process.
_pytest.tmpdir support for providing temporary directories to test functions.
_pytest.unittest discovery and running of std-library “unittest” style tests.
77
78 Chapter 4. pytest default plugin reference

CHAPTER
FIVE
PYTEST HOOK REFERENCE
5.1 Hook specification and validation
pytest calls hook functions to implement initialization, running, test execution and reporting. When pytest loads
a plugin it validates that each hook function conforms to its respective hook specification. Each hook function name
and its argument names need to match a hook specification. However, a hook function may accept fewer parameters
by simply not specifying them. If you mistype argument names or the hook name itself you get an error showing the
available arguments.
5.2 Initialization, command line and configuration hooks
pytest_load_initial_conftests(args, early_config, parser)

implements the loading of initial conftest files ahead of command line option parsing.
pytest_cmdline_preparse(config, args)
(deprecated) modify command line arguments before option parsing.
pytest_cmdline_parse(pluginmanager, args)
return initialized config object, parsing the specified args.
pytest_namespace()
return dict of name->object to be made globally available in the pytest namespace. This hook is called before
command line options are parsed.
pytest_addoption(parser)
register argparse-style options and ini-style config values.
This function must be implemented in a plugin and is called once at the beginning of a test run.
Parameters parser – To add command line options, call parser.addoption(...). To add
ini-file values call parser.addini(...).
Options can later be accessed through the config object, respectively:
•config.getoption(name) to retrieve the value of a command line option.
•config.getini(name) to retrieve a value read from an ini-style file.
The config object is passed around on many internal objects via the .config attribute or can be retrieved as
the pytestconfig fixture or accessed via (deprecated) pytest.config.
pytest_cmdline_main(config)
called for performing the main command line action. The default implementation will invoke the configure
hooks and runtest_mainloop.
79
pytest_configure(config)
called after command line options have been parsed and all plugins and initial conftest files been loaded.
pytest_unconfigure(config)
called before test process is exited.
5.3 Generic “runtest” hooks
All runtest related hooks receive a pytest.Item object.

pytest_runtest_protocol(item, nextitem)
implements the runtest_setup/call/teardown protocol for the given test item, including capturing exceptions and
calling reporting hooks.
Parameters
• item – test item for which the runtest protocol is performed.
• nextitem – the scheduled-to-be-next test item (or None if this is the end my friend). This
argument is passed on to pytest_runtest_teardown().
Return boolean True if no further hook implementations should be invoked.
pytest_runtest_setup(item)
called before pytest_runtest_call(item).
pytest_runtest_call(item)
called to execute the test item.
pytest_runtest_teardown(item, nextitem)
called after pytest_runtest_call.
Parameters nextitem – the scheduled-to-be-next test item (None if no further test item is sched-
uled). This argument can be used to perform exact teardowns, i.e. calling just enough finalizers
so that nextitem only needs to call setup-functions.
pytest_runtest_makereport(item, call)
return a _pytest.runner.TestReport object for the given pytest.Item and
_pytest.runner.CallInfo.
For deeper understanding you may look at the default implementation of these hooks in _pytest.runner and
maybe also in _pytest.pdb which interacts with _pytest.capture and its input/output capturing in order to
immediately drop into interactive debugging when a test failure occurs.
The _pytest.terminal reported specifically uses the reporting hook to print information about a test run.
5.4 Collection hooks
pytest calls the following hooks for collecting files and directories:
pytest_ignore_collect(path, config)
return True to prevent considering this path for collection. This hook is consulted for all files and directories
prior to calling more specific hooks.
pytest_collect_directory(path, parent)
called before traversing a directory for collection files.
80 Chapter 5. pytest hook reference

pytest_collect_file(path, parent)
return collection Node or None for the given path. Any new node needs to have the specified parent as a
parent.
For influencing the collection of objects in Python modules you can use the following hook:
pytest_pycollect_makeitem(collector, name, obj)
return custom item/collector for a python object in a module, or None.
pytest_generate_tests(metafunc)
generate (multiple) parametrized calls to a test function.
After collection is complete, you can modify the order of items, delete or otherwise amend the test items:
pytest_collection_modifyitems(session, config, items)
called after collection has been performed, may filter or re-order the items in-place.
5.5 Reporting hooks
Session related reporting hooks:

pytest_collectstart(collector)
collector starts collecting.
pytest_itemcollected(item)
we just collected a test item.
pytest_collectreport(report)
collector finished collecting.
pytest_deselected(items)
called for test items deselected by keyword.
And here is the central hook for reporting about test execution:
pytest_runtest_logreport(report)
process a test setup/call/teardown report relating to the respective phase of executing a test.
5.6 Debugging/Interaction hooks
There are few hooks which can be used for special reporting or interaction with exceptions:
pytest_internalerror(excrepr, excinfo)
called for internal errors.
pytest_keyboard_interrupt(excinfo)
called for keyboard interrupt.
pytest_exception_interact(node, call, report)
(experimental, new in 2.4) called when an exception was raised which can potentially be interactively handled.
This hook is only called if an exception was raised that is not an internal exception like “skip.Exception”.
5.7 Declaring new hooks
Plugins and conftest.py files may declare new hooks that can then be implemented by other plugins in order to
alter behaviour or interact with the new plugin:
5.5. Reporting hooks 81

pytest_addhooks(pluginmanager)
called at plugin load time to allow adding new hooks via a call to pluginmanager.registerhooks(module).
Hooks are usually declared as do-nothing functions that contain only documentation describing when the hook will be
called and what return values are expected.
For an example, see newhooks.py from xdist: pytest distributed testing plugin.
5.8 Using hooks from 3rd party plugins
Using new hooks from plugins as explained above might be a little tricky because the standard Hook specification and
validation mechanism: if you depend on a plugin that is not installed, validation will fail and the error message will
not make much sense to your users.
One approach is to defer the hook implementation to a new plugin instead of declaring the hook functions directly in
your plugin module, for example:
# contents of myplugin.py
class DeferPlugin(object):
"""Simple plugin to defer pytest-xdist hook functions."""
def pytest_testnodedown(self, node, error):

"""standard xdist hook function.
"""
def pytest_configure(config):
if config.pluginmanager.hasplugin('xdist'):
config.pluginmanager.register(DeferPlugin())
This has the added benefit of allowing you to conditionally install hooks depending on which plugins are installed.
5.9 hookwrapper: executing around other hooks
New in version 2.7: (experimental)

pytest plugins can implement hook wrappers which which wrap the execution of other hook implementations. A hook
wrapper is a generator function which yields exactly once. When pytest invokes hooks it first executes hook wrappers
and passes the same arguments as to the regular hooks.
At the yield point of the hook wrapper pytest will execute the next hook implementations and return their result to the
yield point in the form of a CallOutcome instance which encapsulates a result or exception info. The yield point
itself will thus typically not raise exceptions (unless there are bugs).
Here is an example definition of a hook wrapper:
import pytest
@pytest.mark.hookwrapper
def pytest_pyfunc_call(pyfuncitem):
# do whatever you want before the next hook executes
outcome = yield
# outcome.excinfo may be None or a (cls, val, tb) tuple
res = outcome.get_result() # will raise if outcome was exception
# postprocess result

Note that hook wrappers don’t return results themselves, they merely perform tracing or other side effects around the
actual hook implementations. If the result of the underlying hook is a mutable object, they may modify that result,
however.
5.9. hookwrapper: executing around other hooks 83


CHAPTER
SIX
REFERENCE OF OBJECTS INVOLVED IN HOOKS
class Config
access to configuration values, pluginmanager and plugin hooks.
option = None
access to command line option as attributes. (deprecated), use getoption() instead
pluginmanager = None
a pluginmanager instance
warn(code, message)
generate a warning for this test session.
classmethod fromdictargs(option_dict, args)
constructor useable for subprocesses.
addinivalue_line(name, line)
add a line to an ini-file option. The option must have been declared but might not yet be set in which case
the line becomes the the first line in its value.
getini(name)
return configuration value from an ini file. If the specified name hasn’t been registered through a prior
parser.addini call (usually from a plugin), a ValueError is raised.
getoption(name, default=<NOTSET>, skip=False)
return command line option value.
Parameters
• name – name of the option. You may also specify the literal --OPT option instead of the
“dest” option name.
• default – default value if no option of that name exists.
• skip – if True raise pytest.skip if option does not exists or has a None value.
getvalue(name, path=None)
(deprecated, use getoption())
getvalueorskip(name, path=None)
(deprecated, use getoption(skip=True))
class Parser
Parser for command line arguments and ini-file values.
getgroup(name, description=’‘, after=None)
get (or create) a named option Group.
Name name of the option group.
85
Description long description for –help output.

After name of other group, used for ordering –help output.
The returned group object has an addoption method with the same signature as parser.addoption
but will be shown in the respective group in the output of pytest. --help.
addoption(*opts, **attrs)
register a command line option.
Opts option names, can be short or long options.
Attrs same attributes which the add_option() function of the argparse library accepts.
After command line parsing options are available on the pytest config object via config.option.NAME
where NAME is usually set by passing a dest attribute, for example addoption("--long",
dest="NAME", ...).
addini(name, help, type=None, default=None)
register an ini-file option.
Name name of the ini-variable
Type type of the variable, can be pathlist, args or linelist.
Default default value if no ini-file option exists but is queried.
The value of ini-variables can be retrieved via a call to config.getini(name).
class Node
base class for Collector and Item the test collection tree. Collector subclasses have children, Items are terminal
nodes.
name = None
a unique name within the scope of the parent node
parent = None
the parent collector node.
config = None
the pytest config object
session = None
the session this node is part of
fspath = None
filesystem path where this node was collected from (can be None)
keywords = None
keywords/markers collected from all scopes
extra_keyword_matches = None
allow adding of extra keywords to use for matching
ihook
fspath sensitive hook proxy used to call pytest hooks
warn(code, message)
generate a warning with the given code and message for this item.
nodeid
a ::-separated string denoting its collection tree address.
listchain()
return list of all parent collectors up to self, starting from root of collection tree.
86 Chapter 6. Reference of objects involved in hooks

add_marker(marker)
dynamically add a marker object to the node.
marker can be a string or pytest.mark.* instance.
get_marker(name)
get a marker object from this node or None if the node doesn’t have a marker with that name.
listextrakeywords()
Return a set of all extra keywords in self and any parents.
addfinalizer(fin)
register a function to be called when this node is finalized.
This method can only be called when this node is active in a setup chain, for example during self.setup().
getparent(cls)
get the next parent node (including ourself) which is an instance of the given class
class Collector
Bases: _pytest.main.Node
Collector instances create children through collect() and thus iteratively build a tree.
exception CollectError
Bases: exceptions.Exception
an error during collection, contains a custom message.
Collector.collect()
returns a list of children (items and collectors) for this collection node.
Collector.repr_failure(excinfo)
represent a collection failure.
class Item
Bases: _pytest.main.Node
a basic test invocation item. Note that for a single function there might be multiple test invocation items.
class Module
Bases: _pytest.main.File, _pytest.python.PyCollector
Collector for test classes and functions.
class Class
Bases: _pytest.python.PyCollector
Collector for test methods.
class Function
Bases: _pytest.python.FunctionMixin, _pytest.main.Item,
_pytest.python.FuncargnamesCompatAttr
a Function Item is responsible for setting up and executing a Python test function.
function
underlying python ‘function’ object
runtest()
execute the underlying test function.
class CallInfo
Result/Exception info a function invocation.
87
when = None
context of invocation: one of “setup”, “call”, “teardown”, “memocollect”
excinfo = None
None or ExceptionInfo object.
class TestReport
Basic test report object (also used for setup and teardown calls if they fail).
nodeid = None
normalized collection node id
location = None
a (filesystempath, lineno, domaininfo) tuple indicating the actual location of a test item - it might be
different from the collected one e.g. if a method is inherited from a different module.
keywords = None
a name -> value dictionary containing all keywords and markers associated with a test invocation.
outcome = None
test outcome, always one of “passed”, “failed”, “skipped”.
longrepr = None
None or a failure representation.
when = None
one of ‘setup’, ‘call’, ‘teardown’ to indicate runtest phase.
sections = None
list of (secname, data) extra information which needs to marshallable
duration = None
time it took to run just the test
class CallOutcome
Outcome of a function call, either an exception or a proper result. Calling the get_result method will return
the result or reraise the exception raised when the function was called.
88 Chapter 6. Reference of objects involved in hooks

CHAPTER
SEVEN
LIST OF THIRD-PARTY PLUGINS
The table below contains a listing of plugins found in PyPI and their status when tested using py.test 2.7.0 and python
2.7 and 3.3.
A complete listing can also be found at plugincompat, which contains tests status against other py.test releases.
Name Py27 Py34 Home Summary
pytest-allure-adaptor Plugin for py.test to generate allure xml reports
pytest-ansible UNKNOWN
pytest-autochecklog automatically check condition and log all the checks
pytest-bdd BDD for pytest

pytest-beakerlib link A pytest plugin that reports test results to the BeakerLib framework
pytest-beds Fixtures for testing Google Appengine (GAE) apps
pytest-bench Benchmark utility that plugs into pytest.
pytest-benchmark py.test fixture for benchmarking code
pytest-blockage Disable network requests during a test run.
pytest-bpdb A py.test plug-in to enable drop to bpdb debugger on test failure.
pytest-browsermob-proxy BrowserMob proxy plugin for py.test.
pytest-bugzilla py.test bugzilla integration plugin
pytest-cache pytest plugin with mechanisms for caching across test runs
pytest-cagoule Pytest plugin to only run tests affected by changes
pytest-capturelog py.test plugin to capture log messages
pytest-catchlog py.test plugin to catch log messages. This is a fork of pytest-capturelog.
pytest-circleci py.test plugin for CircleCI
pytest-cloud Distributed tests planner plugin for pytest testing framework.
pytest-codecheckers pytest plugin to add source code sanity checks (pep8 and friends)
89
Table 7.1 – continued from previous page

pytest-colordots Colorizes the progress indicators
pytest-config Base configurations and utilities for developing your Python project test
pytest-contextfixture Define pytest fixtures as context managers.
pytest-couchdbkit py.test extension for per-test couchdb databases using couchdbkit
pytest-cov py.test plugin for coverage reporting with support for both centralised an
pytest-cpp Use pytest’s runner to discover and execute C++ tests
pytest-dbfixtures Databases fixtures plugin for py.test.
pytest-dbus-notification D-BUS notifications for pytest results.
pytest-describe Describe-style plugin for pytest
pytest-diffeo Common py.test support for Diffeo packages

pytest-django link A Django plugin for py.test.
pytest-django-haystack Cleanup your Haystack indexes between tests
pytest-django-lite The bare minimum to integrate py.test with Django.
pytest-django-sqlcount py.test plugin for reporting the number of SQLs executed per django test
pytest-echo link pytest plugin with mechanisms for echoing environment variables, packa
pytest-env py.test plugin that allows you to add environment variables.
pytest-eradicate pytest plugin to check for commented out code
pytest-figleaf py.test figleaf coverage plugin

pytest-fixture-tools ? Plugin for pytest which provides tools for fixtures
pytest-flakes pytest plugin to check source code with pyflakes
pytest-flask A set of py.test fixtures to test Flask applications.

pytest-greendots ? Green progress dots
pytest-growl ? Growl notifications for pytest results.
pytest-httpbin Easily test your HTTP library against a local copy of httpbin
pytest-httpretty A thin wrapper of HTTPretty for pytest
pytest-incremental an incremental test runner (pytest plugin)
pytest-instafail py.test plugin to show failures instantly
pytest-ipdb A py.test plug-in to enable drop to ipdb debugger on test failure.
pytest-ipynb Use pytest’s runner to discover and execute tests as cells of IPython note
90 Chapter 7. List of Third-Party Plugins


pytest-jira py.test JIRA integration plugin, using markers
pytest-knows A pytest plugin that can automaticly skip test case based on dependence
pytest-konira Run Konira DSL tests with py.test
pytest-localserver py.test plugin to test server connections locally.
pytest-marker-bugzilla py.test bugzilla integration plugin, using markers
pytest-markfiltration UNKNOWN
pytest-marks UNKNOWN
pytest-mock Thin-wrapper around the mock package for easier use with py.test
pytest-monkeyplus pytest’s monkeypatch subclass with extra functionalities
pytest-mozwebqa Mozilla WebQA plugin for py.test.

pytest-multihost link Utility for writing multi-host tests for pytest
pytest-oerp pytest plugin to test OpenERP modules

pytest-oot link Run object-oriented tests in a simple format
pytest-optional include/exclude values of fixtures in pytest
pytest-ordering pytest plugin to run your tests in a specific order
pytest-osxnotify OS X notifications for py.test results.

pytest-paste-config ? Allow setting the path to a paste config file
pytest-pep257 ? py.test plugin for pep257
pytest-pep8 pytest plugin to check PEP8 requirements
pytest-pipeline Pytest plugin for functional testing of data analysis pipelines
pytest-poo Visualize your crappy tests
pytest-poo-fail Visualize your failed tests with poo
pytest-pycharm Plugin for py.test to enter PyCharm debugger on uncaught exceptions
pytest-pydev py.test plugin to connect to a remote debug server with PyDev or PyCha
pytest-pyq link Pytest fixture “q” for pyq
pytest-pythonpath pytest plugin for adding to the PYTHONPATH from command line or co
pytest-qt pytest support for PyQt and PySide applications
pytest-quickcheck pytest plugin to generate random data inspired by QuickCheck
pytest-rage pytest plugin to implement PEP712
91

pytest-raisesregexp Simple pytest plugin to look for regex in Exceptions
pytest-random py.test plugin to randomize tests
pytest-readme Test your README.md file

pytest-regtest link py.test plugin for regression tests
pytest-remove-stale-bytecode py.test plugin to remove stale byte code files.
pytest-rerunfailures py.test plugin to re-run tests to eliminate flakey failures
pytest-runfailed implement a –failed option for pytest
pytest-runner Invoke py.test as distutils command with dependency resolution.
pytest-services Services plugin for pytest testing framework
pytest-sftpserver py.test plugin to locally test sftp server connections.
pytest-smartcov Smart coverage plugin for pytest.

pytest-sourceorder link Test-ordering plugin for pytest
pytest-spec pytest plugin to display test execution output like a SPECIFICATION
pytest-splinter Splinter plugin for pytest testing framework
pytest-stepwise Run a test suite one failing test at a time.
pytest-sugar py.test is a plugin for py.test that changes the default look and feel of py.
pytest-timeout py.test plugin to abort hanging tests
pytest-tornado A py.test plugin providing fixtures and markers to simplify testing of asy
pytest-translations Test your translation files
pytest-twisted A twisted plugin for py.test.
pytest-unmarked Run only unmarked tests
pytest-watch Local continuous test runner with pytest and watchdog.
pytest-xdist py.test xdist plugin for distributed testing and loop-on-failing modes
pytest-xprocess pytest plugin to manage external processes across test runs

pytest-yamlwsgi ? Run tests against wsgi apps defined in yaml
pytest-zap OWASP ZAP plugin for py.test.
(Updated on 2015-02-28)
92 Chapter 7. List of Third-Party Plugins

CHAPTER
EIGHT
USAGES AND EXAMPLES
Here is a (growing) list of examples. Contact us if you need more examples or have questions. Also take a look at
the comprehensive documentation which contains many example snippets as well. Also, pytest on stackoverflow.com
often comes with example answers.
For basic examples, see
• Installation and Getting Started for basic introductory examples
• Asserting with the assert statement for basic assertion examples
• pytest fixtures: explicit, modular, scalable for basic fixture/setup examples
• Parametrizing fixtures and test functions for basic test function parametrization
• Support for unittest.TestCase / Integration of fixtures for basic unittest integration
• Running tests written for nose for basic nosetests integration
The following examples aim at various use cases you might encounter.
8.1 Demo of Python failure reports with pytest
Here is a nice run of several tens of failures and how pytest presents things (unfortunately not showing the nice
colors here in the HTML that you get on the terminal - we are working on that):
assertion $ py.test failure_demo.py
collected 42 items
failure_demo.py FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
================================= FAILURES =================================

____________________________ test_generative[0] ____________________________
param1 = 3, param2 = 6
def test_generative(param1, param2):

> assert param1 * 2 < param2
E assert (3 * 2) < 6
failure_demo.py:15: AssertionError
_________________________ TestFailing.test_simple __________________________
93
self = <failure_demo.TestFailing object at 0x7f65f1ca25c0>
def test_simple(self):
def f():
return 42
def g():
return 43
> assert f() == g()

E assert 42 == 43
E + where 42 = <function TestFailing.test_simple.<locals>.f at 0x7f65f2315510>()
E + and 43 = <function TestFailing.test_simple.<locals>.g at 0x7f65f2323510>()
____________________ TestFailing.test_simple_multiline _____________________
self = <failure_demo.TestFailing object at 0x7f65f1c812b0>
def test_simple_multiline(self):
otherfunc_multi(
42,
> 6*9)
failure_demo.py:33:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
a = 42, b = 54
def otherfunc_multi(a,b):
> assert (a ==
b)
E assert 42 == 54
___________________________ TestFailing.test_not ___________________________
self = <failure_demo.TestFailing object at 0x7f65f1c9df98>
def test_not(self):
def f():
return 42
> assert not f()
E assert not 42
E + where 42 = <function TestFailing.test_not.<locals>.f at 0x7f65f2323598>()
_________________ TestSpecialisedExplanations.test_eq_text _________________
self = <failure_demo.TestSpecialisedExplanations object at 0x7f65f1c67710>
def test_eq_text(self):
> assert 'spam' == 'eggs'
E assert 'spam' == 'eggs'
E - spam
E + eggs
_____________ TestSpecialisedExplanations.test_eq_similar_text _____________
94 Chapter 8. Usages and Examples

def test_eq_similar_text(self):
> assert 'foo 1 bar' == 'foo 2 bar'
E assert 'foo 1 bar' == 'foo 2 bar'
E - foo 1 bar
E ? ^
E + foo 2 bar
E ? ^
____________ TestSpecialisedExplanations.test_eq_multiline_text ____________
self = <failure_demo.TestSpecialisedExplanations object at 0x7f65f1cc4d30>
def test_eq_multiline_text(self):
> assert 'foo\nspam\nbar' == 'foo\neggs\nbar'
E assert 'foo\nspam\nbar' == 'foo\neggs\nbar'
E foo
E - spam
E + eggs
E bar
______________ TestSpecialisedExplanations.test_eq_long_text _______________
self = <failure_demo.TestSpecialisedExplanations object at 0x7f65f1cce588>
def test_eq_long_text(self):
a = '1'*100 + 'a' + '2'*100
b = '1'*100 + 'b' + '2'*100
> assert a == b
E assert '111111111111...2222222222222' == '1111111111111...2222222222222'
E Skipping 90 identical leading characters in diff, use -v to show
E Skipping 91 identical trailing characters in diff, use -v to show
E - 1111111111a222222222
E ? ^
E + 1111111111b222222222
E ? ^
_________ TestSpecialisedExplanations.test_eq_long_text_multiline __________
self = <failure_demo.TestSpecialisedExplanations object at 0x7f65f1c81cc0>
def test_eq_long_text_multiline(self):
a = '1\n'*100 + 'a' + '2\n'*100
b = '1\n'*100 + 'b' + '2\n'*100
> assert a == b
E assert '1\n1\n1\n1\n...n2\n2\n2\n2\n' == '1\n1\n1\n1\n1...n2\n2\n2\n2\n'
E Skipping 190 identical leading characters in diff, use -v to show
E Skipping 191 identical trailing characters in diff, use -v to show
E 1
E 1
E 1
E 1
E 1
E - a2
8.1. Demo of Python failure reports with pytest 95

E + b2
E 2
E 2
E 2
E 2
_________________ TestSpecialisedExplanations.test_eq_list _________________
self = <failure_demo.TestSpecialisedExplanations object at 0x7f65f1ca2cc0>
def test_eq_list(self):
> assert [0, 1, 2] == [0, 1, 3]
E assert [0, 1, 2] == [0, 1, 3]
E At index 2 diff: 2 != 3
______________ TestSpecialisedExplanations.test_eq_list_long _______________
def test_eq_list_long(self):
a = [0]*100 + [1] + [3]*100
b = [0]*100 + [2] + [3]*100
> assert a == b
E assert [0, 0, 0, 0, 0, 0, ...] == [0, 0, 0, 0, 0, 0, ...]
E At index 100 diff: 1 != 2
_________________ TestSpecialisedExplanations.test_eq_dict _________________
self = <failure_demo.TestSpecialisedExplanations object at 0x7f65f1c9b588>
def test_eq_dict(self):
> assert {'a': 0, 'b': 1, 'c': 0} == {'a': 0, 'b': 2, 'd': 0}
E assert {'a': 0, 'b': 1, 'c': 0} == {'a': 0, 'b': 2, 'd': 0}
E Omitting 1 identical items, use -v to show
E Differing items:
E {'b': 1} != {'b': 2}
E Left contains more items:
E {'c': 0}
E Right contains more items:
E {'d': 0}
_________________ TestSpecialisedExplanations.test_eq_set __________________
self = <failure_demo.TestSpecialisedExplanations object at 0x7f65f1c7fdd8>
def test_eq_set(self):
> assert set([0, 10, 11, 12]) == set([0, 20, 21])
E assert set([0, 10, 11, 12]) == set([0, 20, 21])
E Extra items in the left set:
E 10
E 11

E 12
E Extra items in the right set:
E 20
E 21
_____________ TestSpecialisedExplanations.test_eq_longer_list ______________
self = <failure_demo.TestSpecialisedExplanations object at 0x7f65f1c347f0>
def test_eq_longer_list(self):
> assert [1,2] == [1,2,3]
E assert [1, 2] == [1, 2, 3]
E Right contains more items, first extra item: 3
_________________ TestSpecialisedExplanations.test_in_list _________________
self = <failure_demo.TestSpecialisedExplanations object at 0x7f65f2313668>
def test_in_list(self):
> assert 1 in [0, 2, 3, 4, 5]
E assert 1 in [0, 2, 3, 4, 5]
__________ TestSpecialisedExplanations.test_not_in_text_multiline __________
self = <failure_demo.TestSpecialisedExplanations object at 0x7f65f1cceb38>
def test_not_in_text_multiline(self):
text = 'some multiline\ntext\nwhich\nincludes foo\nand a\ntail'
> assert 'foo' not in text
E assert 'foo' not in 'some multiline\ntext\nw...ncludes foo\nand a\ntail'
E 'foo' is contained here:
E some multiline
E text
E which
E includes foo
E ? +++
E and a
E tail
___________ TestSpecialisedExplanations.test_not_in_text_single ____________
def test_not_in_text_single(self):
text = 'single foo line'
E assert 'foo' not in 'single foo line'
E single foo line
E ? +++

_________ TestSpecialisedExplanations.test_not_in_text_single_long _________
self = <failure_demo.TestSpecialisedExplanations object at 0x7f65f1c9d4e0>
def test_not_in_text_single_long(self):
text = 'head ' * 50 + 'foo ' + 'tail ' * 20
E assert 'foo' not in 'head head head head hea...ail tail tail tail tail '
E head head foo tail tail tail tail tail tail tail tail tail tail tail tail tail tail tail
E ? +++
______ TestSpecialisedExplanations.test_not_in_text_single_long_term _______
self = <failure_demo.TestSpecialisedExplanations object at 0x7f65f1ce16d8>
def test_not_in_text_single_long_term(self):
text = 'head ' * 50 + 'f'*70 + 'tail ' * 20
> assert 'f'*70 not in text
E assert 'fffffffffff...ffffffffffff' not in 'head head he...l tail tail '
E 'ffffffffffffffffff...fffffffffffffffffff' is contained here:
E head head fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffftail tail
E ? ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
______________________________ test_attribute ______________________________
def test_attribute():
class Foo(object):
b = 1
i = Foo()
> assert i.b == 2
E assert 1 == 2
E + where 1 = <failure_demo.test_attribute.<locals>.Foo object at 0x7f65f1c814e0>.b
_________________________ test_attribute_instance __________________________
def test_attribute_instance():
class Foo(object):
b = 1
> assert Foo().b == 2
E assert 1 == 2
E + where 1 = <failure_demo.test_attribute_instance.<locals>.Foo object at 0x7f65f1c7f7f0>.b
E + where <failure_demo.test_attribute_instance.<locals>.Foo object at 0x7f65f1c7f7f0> = <c
__________________________ test_attribute_failure __________________________
def test_attribute_failure():
class Foo(object):
def _get_b(self):
raise Exception('Failed to get attrib')
b = property(_get_b)
i = Foo()
> assert i.b == 2

failure_demo.py:116:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
self = <failure_demo.test_attribute_failure.<locals>.Foo object at 0x7f65f1c97dd8>
def _get_b(self):
> raise Exception('Failed to get attrib')
E Exception: Failed to get attrib
failure_demo.py:113: Exception
_________________________ test_attribute_multiple __________________________
def test_attribute_multiple():
class Foo(object):
b = 1
class Bar(object):
b = 2
> assert Foo().b == Bar().b
E assert 1 == 2
E + where 1 = <failure_demo.test_attribute_multiple.<locals>.Foo object at 0x7f65f1c9b630>.b
E + where <failure_demo.test_attribute_multiple.<locals>.Foo object at 0x7f65f1c9b630> = <c
E + and 2 = <failure_demo.test_attribute_multiple.<locals>.Bar object at 0x7f65f1c9b2b0>.b
E + where <failure_demo.test_attribute_multiple.<locals>.Bar object at 0x7f65f1c9b2b0> = <c
__________________________ TestRaises.test_raises __________________________
self = <failure_demo.TestRaises object at 0x7f65f1c3eba8>
def test_raises(self):
s = 'qwe'
> raises(TypeError, "int(s)")
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
> int(s)
E ValueError: invalid literal for int() with base 10: 'qwe'
<0-codegen /tmp/sandbox/pytest/.tox/regen/lib/python3.4/site-packages/_pytest/python.py:1075>:1: Valu

______________________ TestRaises.test_raises_doesnt _______________________
self = <failure_demo.TestRaises object at 0x7f65f1cc4eb8>
def test_raises_doesnt(self):
> raises(IOError, "int('3')")
E Failed: DID NOT RAISE
failure_demo.py:136: Failed
__________________________ TestRaises.test_raise ___________________________
self = <failure_demo.TestRaises object at 0x7f65f1cceeb8>
def test_raise(self):
> raise ValueError("demo error")
E ValueError: demo error
failure_demo.py:139: ValueError

________________________ TestRaises.test_tupleerror ________________________
self = <failure_demo.TestRaises object at 0x7f65f23136d8>
def test_tupleerror(self):
> a,b = [1]
E ValueError: need more than 1 value to unpack
______ TestRaises.test_reinterpret_fails_with_print_for_the_fun_of_it ______
self = <failure_demo.TestRaises object at 0x7f65f1ca2240>
def test_reinterpret_fails_with_print_for_the_fun_of_it(self):
l = [1,2,3]
print ("l is %r" % l)
> a,b = l.pop()
E TypeError: 'int' object is not iterable
failure_demo.py:147: TypeError
l is [1, 2, 3]
________________________ TestRaises.test_some_error ________________________
self = <failure_demo.TestRaises object at 0x7f65f1cb36a0>
def test_some_error(self):
> if namenotexi:
E NameError: name 'namenotexi' is not defined
failure_demo.py:150: NameError
____________________ test_dynamic_compile_shows_nicely _____________________
def test_dynamic_compile_shows_nicely():
src = 'def foo():\n assert 1 == 0\n'
name = 'abc-123'
module = py.std.imp.new_module(name)
code = py.code.compile(src, name, 'exec')
py.builtin.exec_(code, module.__dict__)
py.std.sys.modules[name] = module
> module.foo()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
def foo():
> assert 1 == 0
E assert 1 == 0
<2-codegen 'abc-123' /tmp/sandbox/pytest/doc/en/example/assertion/failure_demo.py:162>:2: AssertionEr

____________________ TestMoreErrors.test_complex_error _____________________
self = <failure_demo.TestMoreErrors object at 0x7f65f1cb5470>
def test_complex_error(self):
def f():
return 44
def g():

return 43
> somefunc(f(), g())
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
failure_demo.py:8: in somefunc
otherfunc(x,y)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
a = 44, b = 43
def otherfunc(a,b):
> assert a==b
E assert 44 == 43
___________________ TestMoreErrors.test_z1_unpack_error ____________________
self = <failure_demo.TestMoreErrors object at 0x7f65f1c9d940>
def test_z1_unpack_error(self):
l = []
> a,b = l
E ValueError: need more than 0 values to unpack
____________________ TestMoreErrors.test_z2_type_error _____________________
self = <failure_demo.TestMoreErrors object at 0x7f65f1c7f208>
def test_z2_type_error(self):
l = 3
> a,b = l
E TypeError: 'int' object is not iterable
failure_demo.py:183: TypeError
______________________ TestMoreErrors.test_startswith ______________________
self = <failure_demo.TestMoreErrors object at 0x7f65f1cc40b8>
def test_startswith(self):
s = "123"
g = "456"
> assert s.startswith(g)
E assert <built-in method startswith of str object at 0x7f65f1ce14c8>('456')
E + where <built-in method startswith of str object at 0x7f65f1ce14c8> = '123'.startswith
__________________ TestMoreErrors.test_startswith_nested ___________________
self = <failure_demo.TestMoreErrors object at 0x7f65f1c81b00>
def test_startswith_nested(self):
def f():
return "123"
def g():
return "456"
> assert f().startswith(g())

E assert <built-in method startswith of str object at 0x7f65f1ce14c8>('456')

E + where <built-in method startswith of str object at 0x7f65f1ce14c8> = '123'.startswith
E + where '123' = <function TestMoreErrors.test_startswith_nested.<locals>.f at 0x7f65f1c32
E + and '456' = <function TestMoreErrors.test_startswith_nested.<locals>.g at 0x7f65f1c32ea
_____________________ TestMoreErrors.test_global_func ______________________
self = <failure_demo.TestMoreErrors object at 0x7f65f1c97240>
def test_global_func(self):
> assert isinstance(globf(42), float)
E assert isinstance(43, float)
E + where 43 = globf(42)
_______________________ TestMoreErrors.test_instance _______________________
self = <failure_demo.TestMoreErrors object at 0x7f65f1ce1080>
def test_instance(self):
self.x = 6*7
> assert self.x != 42
E assert 42 != 42
E + where 42 = <failure_demo.TestMoreErrors object at 0x7f65f1ce1080>.x
_______________________ TestMoreErrors.test_compare ________________________
self = <failure_demo.TestMoreErrors object at 0x7f65f1c3e828>
def test_compare(self):
> assert globf(10) < 5
E assert 11 < 5
E + where 11 = globf(10)
_____________________ TestMoreErrors.test_try_finally ______________________
self = <failure_demo.TestMoreErrors object at 0x7f65f1c67828>
def test_try_finally(self):
x = 1
try:
> assert x == 0
E assert 1 == 0
___________________ TestCustomAssertMsg.test_single_line ___________________
self = <failure_demo.TestCustomAssertMsg object at 0x7f65f1c29860>
def test_single_line(self):
class A:
a = 1
b = 2
> assert A.a == b, "A.a appears not to be b"
E AssertionError: A.a appears not to be b

E assert 1 == 2
E + where 1 = <class 'failure_demo.TestCustomAssertMsg.test_single_line.<locals>.A'>.a
____________________ TestCustomAssertMsg.test_multiline ____________________
self = <failure_demo.TestCustomAssertMsg object at 0x7f65f1c676a0>
def test_multiline(self):
class A:
a = 1
b = 2
> assert A.a == b, "A.a appears not to be b\n" \
"or does not appear to be b\none of those"
E AssertionError: A.a appears not to be b
E or does not appear to be b
E one of those
E assert 1 == 2
E + where 1 = <class 'failure_demo.TestCustomAssertMsg.test_multiline.<locals>.A'>.a
___________________ TestCustomAssertMsg.test_custom_repr ___________________
self = <failure_demo.TestCustomAssertMsg object at 0x7f65f1ccebe0>
def test_custom_repr(self):
class JSON:
a = 1
def __repr__(self):
return "This is JSON\n{\n 'foo': 'bar'\n}"
a = JSON()
b = 2
> assert a.a == b, a
E AssertionError: This is JSON
E {
E 'foo': 'bar'
E }
E assert 1 == 2
E + where 1 = This is JSON\n{\n 'foo': 'bar'\n}.a
======================== 42 failed in 0.35 seconds =========================
8.2 Basic patterns and examples
8.2.1 Pass different values to a test function, depending on command line options
Suppose we want to write a test that depends on a command line option. Here is a basic pattern how to achieve this:
# content of test_sample.py
def test_answer(cmdopt):
if cmdopt == "type1":
print ("first")
elif cmdopt == "type2":
print ("second")
assert 0 # to see what was printed
8.2. Basic patterns and examples 103

For this to work we need to add a command line option and provide the cmdopt through a fixture function:
import pytest
parser.addoption("--cmdopt", action="store", default="type1",
help="my option: type1 or type2")
@pytest.fixture
def cmdopt(request):
return request.config.getoption("--cmdopt")
Let’s run this without supplying our new option:

$ py.test -q test_sample.py
F
================================= FAILURES =================================
_______________________________ test_answer ________________________________
cmdopt = 'type1'
print ("first")
print ("second")
> assert 0 # to see what was printed
E assert 0
first
And now with supplying a command line option:

$ py.test -q --cmdopt=type2
F
================================= FAILURES =================================
_______________________________ test_answer ________________________________
cmdopt = 'type2'
print ("first")
print ("second")
> assert 0 # to see what was printed
E assert 0
second
You can see that the command line option arrived in our test. This completes the basic pattern. However, one often

rather wants to process command line options outside of the test and rather pass in different or more complex objects.
8.2.2 Dynamically adding command line options
Through addopts you can statically add command line options for your project. You can also dynamically modify
the command line arguments before they get processed:
import sys
def pytest_cmdline_preparse(args):
if 'xdist' in sys.modules: # pytest-xdist plugin
import multiprocessing
num = max(multiprocessing.cpu_count() / 2, 1)
args[:] = ["-n", str(num)] + args
If you have the xdist plugin installed you will now always perform test runs using a number of subprocesses close to
your CPU. Running in an empty directory with the above conftest.py:
$ py.test
collected 0 items
============================= in 0.00 seconds =============================
8.2.3 Control skipping of tests according to command line option
Here is a conftest.py file adding a --runslow command line option to control skipping of slow marked tests:
import pytest
parser.addoption("--runslow", action="store_true",
help="run slow tests")
if 'slow' in item.keywords and not item.config.getoption("--runslow"):
pytest.skip("need --runslow option to run")
We can now write a test module like this:

import pytest
slow = pytest.mark.slow
def test_func_fast():
pass
@slow
def test_func_slow():
pass
and when running it will see a skipped “slow” test:

$ py.test -rs # "-rs" means report details on the little 's'

collected 2 items
test_module.py .s
SKIP [1] /tmp/doc-exec-162/conftest.py:9: need --runslow option to run
=================== 1 passed, 1 skipped in 0.01 seconds ====================
Or run it including the slow marked test:

$ py.test --runslow
collected 2 items
test_module.py ..
8.2.4 Writing well integrated assertion helpers
If you have a test helper function called from a test you can use the pytest.fail marker to fail a test with a certain
message. The test support function will not show up in the traceback if you set the __tracebackhide__ option
somewhere in the helper function. Example:
# content of test_checkconfig.py
import pytest
def checkconfig(x):
__tracebackhide__ = True
if not hasattr(x, "config"):
pytest.fail("not configured: %s" %(x,))
def test_something():
checkconfig(42)
The __tracebackhide__ setting influences pytest showing of tracebacks: the checkconfig function will
not be shown unless the --fulltrace command line option is specified. Let’s run our little function:
$ py.test -q test_checkconfig.py
F
================================= FAILURES =================================
______________________________ test_something ______________________________
def test_something():
> checkconfig(42)
E Failed: not configured: 42
test_checkconfig.py:8: Failed

8.2.5 Detect if running from within a pytest run
Usually it is a bad idea to make application code behave differently if called from a test. But if you absolutely must
find out if your application code is running from a test you can do something like this:
import sys
sys._called_from_test = True
def pytest_unconfigure(config):
del sys._called_from_test
and then check for the sys._called_from_test flag:

if hasattr(sys, '_called_from_test'):
# called from within a test run
else:
# called "normally"
accordingly in your application. It’s also a good idea to use your own application module rather than sys for handling
flag.
8.2.6 Adding info to test report header
It’s easy to present extra information in a pytest run:

def pytest_report_header(config):
return "project deps: mylib-1.1"
which will add the string to the test header accordingly:

$ py.test
project deps: mylib-1.1
collected 0 items
============================= in 0.00 seconds =============================
You can also return a list of strings which will be considered as several lines of information. You can of course also
make the amount of reporting information on e.g. the value of config.option.verbose so that you present
more information appropriately:
def pytest_report_header(config):
if config.option.verbose > 0:
return ["info1: did you know that ...", "did you?"]
which will add info only when run with “–v”:

$ py.test -v


info1: did you know that ...
did you?
============================= in 0.00 seconds =============================
and nothing when run plainly:

$ py.test
collected 0 items
============================= in 0.00 seconds =============================
8.2.7 profiling test duration
If you have a slow running large test suite you might want to find out which tests are the slowest. Let’s make an
artifical test suite:
# content of test_some_are_slow.py
import time
def test_funcfast():
pass
def test_funcslow1():
time.sleep(0.1)
def test_funcslow2():
time.sleep(0.2)
Now we can profile which test functions execute the slowest:

$ py.test --durations=3
collected 3 items
test_some_are_slow.py ...
========================= slowest 3 test durations =========================

0.20s call test_some_are_slow.py::test_funcslow2
0.10s call test_some_are_slow.py::test_funcslow1
0.00s setup test_some_are_slow.py::test_funcslow2
8.2.8 incremental testing - test steps
Sometimes you may have a testing situation which consists of a series of test steps. If one step fails it makes no sense
to execute further steps as they are all expected to fail anyway and their tracebacks add no insight. Here is a simple

conftest.py file which introduces an incremental marker which is to be used on classes:

import pytest
def pytest_runtest_makereport(item, call):

if "incremental" in item.keywords:
if call.excinfo is not None:
parent = item.parent
parent._previousfailed = item
if "incremental" in item.keywords:
previousfailed = getattr(item.parent, "_previousfailed", None)
if previousfailed is not None:
pytest.xfail("previous test failed (%s)" %previousfailed.name)
These two hook implementations work together to abort incremental-marked tests in a class. Here is a test module
example:
# content of test_step.py
import pytest
@pytest.mark.incremental
class TestUserHandling:
def test_login(self):
pass
def test_modification(self):
assert 0
def test_deletion(self):
pass
def test_normal():
pass
If we run this:
$ py.test -rx
collected 4 items
test_step.py .Fx.
================================= FAILURES =================================

____________________ TestUserHandling.test_modification ____________________
self = <test_step.TestUserHandling object at 0x7ff60bbb83c8>
> assert 0
E assert 0
test_step.py:9: AssertionError
XFAIL test_step.py::TestUserHandling::()::test_deletion

reason: previous test failed (test_modification)

============== 1 failed, 2 passed, 1 xfailed in 0.02 seconds ===============
We’ll see that test_deletion was not executed because test_modification failed. It is reported as an
“expected failure”.
8.2.9 Package/Directory-level fixtures (setups)
If you have nested test directories, you can have per-directory fixture scopes by placing fixture functions in a
conftest.py file in that directory You can use all types of fixtures including autouse fixtures which are the equiv-
alent of xUnit’s setup/teardown concept. It’s however recommended to have explicit fixture references in your tests or
test classes rather than relying on implicitely executing setup/teardown functions, especially if they are far away from
the actual tests.
Here is a an example for making a db fixture available in a directory:
# content of a/conftest.py
import pytest
class DB:
pass
def db():
return DB()
and then a test module in that directory:

# content of a/test_db.py
def test_a1(db):
assert 0, db # to show value
another test module:

# content of a/test_db2.py
def test_a2(db):
assert 0, db # to show value
and then a module in a sister directory which will not see the db fixture:
# content of b/test_error.py
def test_root(db): # no db here, will error out
pass
We can run this:

$ py.test
collected 7 items
test_step.py .Fx.
a/test_db.py F
a/test_db2.py F
b/test_error.py E
================================== ERRORS ==================================

_______________________ ERROR at setup of test_root ________________________

file /tmp/doc-exec-162/b/test_error.py, line 1
def test_root(db): # no db here, will error out
fixture 'db' not found
available fixtures: pytestconfig, capsys, recwarn, monkeypatch, tmpdir, capfd
use 'py.test --fixtures [testpath]' for help on them.
/tmp/doc-exec-162/b/test_error.py:1
================================= FAILURES =================================
____________________ TestUserHandling.test_modification ____________________
self = <test_step.TestUserHandling object at 0x7f8ecd5b87f0>
> assert 0
E assert 0
test_step.py:9: AssertionError
_________________________________ test_a1 __________________________________
db = <conftest.DB object at 0x7f8ecdc11470>
def test_a1(db):
> assert 0, db # to show value
E AssertionError: <conftest.DB object at 0x7f8ecdc11470>
E assert 0
a/test_db.py:2: AssertionError
_________________________________ test_a2 __________________________________
db = <conftest.DB object at 0x7f8ecdc11470>
def test_a2(db):
> assert 0, db # to show value
E AssertionError: <conftest.DB object at 0x7f8ecdc11470>
E assert 0
a/test_db2.py:2: AssertionError
========== 3 failed, 2 passed, 1 xfailed, 1 error in 0.05 seconds ==========
The two test modules in the a directory see the same db fixture instance while the one test in the sister-directory b
doesn’t see it. We could of course also define a db fixture in that sister directory’s conftest.py file. Note that
each fixture is only instantiated if there is a test actually needing it (unless you use “autouse” fixture which are always
executed ahead of the first test executing).
8.2.10 post-process test reports / failures
If you want to postprocess test reports and need access to the executing environment you can implement a hook that
gets called when the test “report” object is about to be created. Here we write out all failing test calls and also access
a fixture (if it was used by the test) in case you want to query/look at it during your post processing. In our case we
just write some informations out to a failures file:
import pytest
import os.path

@pytest.mark.tryfirst
def pytest_runtest_makereport(item, call, __multicall__):
# execute all other hooks to obtain the report object
rep = __multicall__.execute()
# we only look at actual failing test calls, not setup/teardown

if rep.when == "call" and rep.failed:
mode = "a" if os.path.exists("failures") else "w"
with open("failures", mode) as f:
# let's also access a fixture for the fun of it
if "tmpdir" in item.funcargs:
extra = " (%s)" % item.funcargs["tmpdir"]
else:
extra = ""
f.write(rep.nodeid + extra + "\n")

return rep
if you then have failing tests:

def test_fail1(tmpdir):
assert 0
def test_fail2():
assert 0
and run them:

$ py.test test_module.py
collected 2 items
test_module.py FF
================================= FAILURES =================================

________________________________ test_fail1 ________________________________
tmpdir = local('/tmp/pytest-22/test_fail10')
def test_fail1(tmpdir):
> assert 0
E assert 0
________________________________ test_fail2 ________________________________
def test_fail2():
> assert 0
E assert 0
you will have a “failures” file which contains the failing test ids:
$ cat failures
test_module.py::test_fail1 (/tmp/pytest-22/test_fail10)

test_module.py::test_fail2
8.2.11 Making test result information available in fixtures
If you want to make test result reports available in fixture finalizers here is a little example implemented via a local
plugin:
import pytest
@pytest.mark.tryfirst
def pytest_runtest_makereport(item, call, __multicall__):
# execute all other hooks to obtain the report object
rep = __multicall__.execute()
# set an report attribute for each phase of a call, which can

# be "setup", "call", "teardown"
setattr(item, "rep_" + rep.when, rep)

return rep
@pytest.fixture
def something(request):
def fin():
# request.node is an "item" because we use the default
# "function" scope
if request.node.rep_setup.failed:
print ("setting up a test failed!", request.node.nodeid)
elif request.node.rep_setup.passed:
if request.node.rep_call.failed:
print ("executing test failed", request.node.nodeid)
if you then have failing tests:

import pytest
@pytest.fixture
def other():
assert 0
def test_setup_fails(something, other):

pass
def test_call_fails(something):
assert 0
def test_fail2():
assert 0
and run it:

$ py.test -s test_module.py
collected 3 items
test_module.py Esetting up a test failed! test_module.py::test_setup_fails

Fexecuting test failed test_module.py::test_call_fails
F
================================== ERRORS ==================================

____________________ ERROR at setup of test_setup_fails ____________________
@pytest.fixture
def other():
> assert 0
E assert 0
================================= FAILURES =================================
_____________________________ test_call_fails ______________________________
something = None
def test_call_fails(something):
> assert 0
E assert 0
________________________________ test_fail2 ________________________________
def test_fail2():
> assert 0
E assert 0
==================== 2 failed, 1 error in 0.02 seconds =====================
You’ll see that the fixture finalizers could use the precise reporting information.
8.2.12 Integrating pytest runner and cx_freeze
If you freeze your application using a tool like cx_freeze in order to distribute it to your end-users, it is a good idea to
also package your test runner and run your tests using the frozen application.
This way packaging errors such as dependencies not being included into the executable can be detected early while
also allowing you to send test files to users so they can run them in their machines, which can be invaluable to obtain
more information about a hard to reproduce bug.
Unfortunately cx_freeze can’t discover them automatically because of pytest‘s use of dynamic module loading,
so you must declare them explicitly by using pytest.freeze_includes():
# contents of setup.py
from cx_Freeze import setup, Executable
import pytest
setup(
name="app_main",

executables=[Executable("app_main.py")],
options={"build_exe":
{
'includes': pytest.freeze_includes()}
},
# ... other options
)
If you don’t want to ship a different executable just in order to run your tests, you can make your program check for a
certain flag and pass control over to pytest instead. For example:
# contents of app_main.py
import sys
if len(sys.argv) > 1 and sys.argv[1] == '--pytest':

import pytest
sys.exit(pytest.main(sys.argv[2:]))
else:
# normal application execution: at this point argv can be parsed
# by your argument-parsing library of choice as usual
...
This makes it convenient to execute your tests from within your frozen application, using standard py.test
command-line options:
$ ./app_main --pytest --verbose --tb=long --junit-xml=results.xml test-suite/
/bin/sh: 1: ./app_main: not found
8.3 Parametrizing tests
pytest allows to easily parametrize test functions. For basic docs, see Parametrizing fixtures and test functions.
In the following we provide some examples using the builtin mechanisms.
8.3.1 Generating parameters combinations, depending on command line
Let’s say we want to execute a test with different computation parameters and the parameter range shall be determined
by a command line argument. Let’s first write a simple (do-nothing) computation test:
# content of test_compute.py
def test_compute(param1):
assert param1 < 4
Now we add a test configuration like this:

parser.addoption("--all", action="store_true",
help="run all combinations")
if 'param1' in metafunc.fixturenames:
if metafunc.config.option.all:
end = 5
8.3. Parametrizing tests 115

else:
end = 2
metafunc.parametrize("param1", range(end))
This means that we only run 2 tests if we do not pass --all:

$ py.test -q test_compute.py
..
We run only two computations, so we see two dots. let’s run the full monty:
$ py.test -q --all
....F
================================= FAILURES =================================
_____________________________ test_compute[4] ______________________________
param1 = 4
def test_compute(param1):
> assert param1 < 4
E assert 4 < 4
test_compute.py:3: AssertionError
As expected when running the full range of param1 values we’ll get an error on the last one.
8.3.2 Different options for test IDs
pytest will build a string that is the test ID for each set of values in a parametrized test. These IDs can be used with
-k to select specific cases to run, and they will also identify the specific case when one is failing. Running pytest with
--collect-only will show the generated IDs.
Numbers, strings, booleans and None will have their usual string representation used in the test ID. For other objects,
pytest will make a string based on the argument name:
# contents of test_time.py
from datetime import datetime, timedelta
testdata = [(datetime(2001, 12, 12), datetime(2001, 12, 11), timedelta(1)),

(datetime(2001, 12, 11), datetime(2001, 12, 12), timedelta(-1)),
]
@pytest.mark.parametrize("a,b,expected", testdata)
def test_timedistance_v0(a, b, expected):
diff = a - b
assert diff == expected
@pytest.mark.parametrize("a,b,expected", testdata, ids=["forward", "backward"])

diff = a - b

def idfn(val):
if isinstance(val, (datetime,)):
# note this wouldn't show any hours/minutes/seconds
return val.strftime('%Y%m%d')
@pytest.mark.parametrize("a,b,expected", testdata, ids=idfn)

diff = a - b
In test_timedistance_v0, we let pytest generate the test IDs.

In test_timedistance_v1, we specified ids as a list of strings which were used as the test IDs. These are
succinct, but can be a pain to maintain.
In test_timedistance_v2, we specified ids as a function that can generate a string representation to make part
of the test ID. So our datetime values use the label generated by idfn, but because we didn’t generate a label for
timedelta objects, they are still using the default pytest representation:
$ py.test test_time.py --collect-only
============================= in 0.00 seconds =============================

ERROR: file not found: test_time.py
8.3.3 A quick port of “testscenarios”
Here is a quick port to run tests configured with test scenarios, an add-on from Robert Collins for the
standard unittest framework. We only have to work a bit to construct the correct arguments for pytest’s
Metafunc.parametrize():
# content of test_scenarios.py
idlist = []
argvalues = []
for scenario in metafunc.cls.scenarios:
idlist.append(scenario[0])
items = scenario[1].items()
argnames = [x[0] for x in items]
argvalues.append(([x[1] for x in items]))
metafunc.parametrize(argnames, argvalues, ids=idlist, scope="class")
scenario1 = ('basic', {'attribute': 'value'})

scenario2 = ('advanced', {'attribute': 'value2'})
class TestSampleWithScenarios:
scenarios = [scenario1, scenario2]
def test_demo1(self, attribute):

assert isinstance(attribute, str)
def test_demo2(self, attribute):

assert isinstance(attribute, str)

this is a fully self-contained example which you can run with:

$ py.test test_scenarios.py
collected 4 items
test_scenarios.py ....
If you just collect tests you’ll also nicely see ‘advanced’ and ‘basic’ as variants for the test function:
$ py.test --collect-only test_scenarios.py
collected 4 items
<Module 'test_scenarios.py'>
<Class 'TestSampleWithScenarios'>
<Instance '()'>
<Function 'test_demo1[basic]'>
<Function 'test_demo2[basic]'>
<Function 'test_demo1[advanced]'>
<Function 'test_demo2[advanced]'>
============================= in 0.01 seconds =============================
Note that we told metafunc.parametrize() that your scenario values should be considered class-scoped. With
pytest-2.3 this leads to a resource-based ordering.
8.3.4 Deferring the setup of parametrized resources
The parametrization of test functions happens at collection time. It is a good idea to setup expensive resources like
DB connections or subprocess only when the actual test is run. Here is a simple example how you can achieve that,
first the actual test requiring a db object:
# content of test_backends.py
import pytest
def test_db_initialized(db):
# a dummy test
if db.__class__.__name__ == "DB2":
pytest.fail("deliberately failing for demo purposes")
We can now add a test configuration that generates two invocations of the test_db_initialized function and
also implements a factory that creates a database object for the actual test invocations:
import pytest
if 'db' in metafunc.fixturenames:
metafunc.parametrize("db", ['d1', 'd2'], indirect=True)
class DB1:
"one database object"

class DB2:
"alternative database object"
@pytest.fixture
def db(request):
if request.param == "d1":
return DB1()
elif request.param == "d2":
return DB2()
else:
raise ValueError("invalid internal test config")
Let’s first see how it looks like at collection time:

$ py.test test_backends.py --collect-only
collected 2 items
<Module 'test_backends.py'>
<Function 'test_db_initialized[d1]'>
<Function 'test_db_initialized[d2]'>
============================= in 0.01 seconds =============================
And then when we run the test:

$ py.test -q test_backends.py
.F
================================= FAILURES =================================
_________________________ test_db_initialized[d2] __________________________
db = <conftest.DB2 object at 0x7f10a071cb38>
def test_db_initialized(db):
# a dummy test
if db.__class__.__name__ == "DB2":
> pytest.fail("deliberately failing for demo purposes")
E Failed: deliberately failing for demo purposes
test_backends.py:6: Failed
The first invocation with db == "DB1" passed while the second with db == "DB2" failed. Our db fixture func-
tion has instantiated each of the DB values during the setup phase while the pytest_generate_tests generated
two according calls to the test_db_initialized during the collection phase.
8.3.5 Parametrizing test methods through per-class configuration
Here is an example pytest_generate_function function implementing a parametrization scheme similar to

Michael Foord’s unittest parameterizer but in a lot less code:
# content of ./test_parametrize.py
import pytest
# called once per each test function
funcarglist = metafunc.cls.params[metafunc.function.__name__]

argnames = list(funcarglist[0])
metafunc.parametrize(argnames, [[funcargs[name] for name in argnames]
for funcargs in funcarglist])
class TestClass:
# a map specifying multiple argument sets for a test method
params = {
'test_equals': [dict(a=1, b=2), dict(a=3, b=3), ],
'test_zerodivision': [dict(a=1, b=0), ],
}
def test_equals(self, a, b):

assert a == b
def test_zerodivision(self, a, b):

pytest.raises(ZeroDivisionError, "a/b")
Our test generator looks up a class-level definition which specifies which argument sets to use for each test function.
Let’s run it:
$ py.test -q
F..
================================= FAILURES =================================
________________________ TestClass.test_equals[2-1] ________________________
self = <test_parametrize.TestClass object at 0x7f878094f630>, a = 1, b = 2
def test_equals(self, a, b):

> assert a == b
E assert 1 == 2
test_parametrize.py:18: AssertionError
8.3.6 Indirect parametrization with multiple fixtures
Here is a stripped down real-life example of using parametrized testing for testing serialization of objects between
different python interpreters. We define a test_basic_objects function which is to be run with different sets of
arguments for its three arguments:
• python1: first python interpreter, run to pickle-dump an object to a file
• python2: second interpreter, run to pickle-load an object from a file
• obj: object to be dumped/loaded
"""
module containing a parametrized tests testing cross-python
serialization via the pickle module.
"""
import py
import pytest
pythonlist = ['python2.6', 'python2.7', 'python3.3']

@pytest.fixture(params=pythonlist)
def python1(request, tmpdir):
picklefile = tmpdir.join("data.pickle")
return Python(request.param, picklefile)

@pytest.fixture(params=pythonlist)
def python2(request, python1):
return Python(request.param, python1.picklefile)
class Python:
def __init__(self, version, picklefile):
self.pythonpath = py.path.local.sysfind(version)
if not self.pythonpath:
pytest.skip("%r not found" %(version,))
self.picklefile = picklefile
def dumps(self, obj):
dumpfile = self.picklefile.dirpath("dump.py")
dumpfile.write(py.code.Source("""
import pickle
f = open(%r, 'wb')
s = pickle.dump(%r, f, protocol=2)
f.close()
""" % (str(self.picklefile), obj)))
py.process.cmdexec("%s %s" %(self.pythonpath, dumpfile))
def load_and_is_true(self, expression):

loadfile = self.picklefile.dirpath("load.py")
loadfile.write(py.code.Source("""
import pickle
f = open(%r, 'rb')
obj = pickle.load(f)
f.close()
res = eval(%r)
if not res:
raise SystemExit(1)
""" % (str(self.picklefile), expression)))
print (loadfile)
py.process.cmdexec("%s %s" %(self.pythonpath, loadfile))
@pytest.mark.parametrize("obj", [42, {}, {1:3},])

def test_basic_objects(python1, python2, obj):
python1.dumps(obj)
python2.load_and_is_true("obj == %s" % obj)
Running it results in some skips if we don’t have all the python interpreters installed and otherwise runs all combina-
tions (5 interpreters times 5 interpreters times 3 objects to serialize/deserialize):
. $ py.test -rs -q multipython.py
...........................
8.3.7 Indirect parametrization of optional implementations/imports
If you want to compare the outcomes of several implementations of a given API, you can write test functions that
receive the already imported implementations and get skipped in case the implementation is not importable/available.
Let’s say we have a “base” implementation and the other (possibly optimized ones) need to provide similar results:
import pytest

def basemod(request):
return pytest.importorskip("base")
@pytest.fixture(scope="session", params=["opt1", "opt2"])

def optmod(request):
return pytest.importorskip(request.param)
And then a base implementation of a simple function:

# content of base.py
def func1():
return 1
And an optimized version:

# content of opt1.py
def func1():
return 1.0001
And finally a little test module:

def test_func1(basemod, optmod):

assert round(basemod.func1(), 3) == round(optmod.func1(), 3)
If you run this with reporting for skips enabled:

$ py.test -rs test_module.py
collected 2 items
test_module.py .s
SKIP [1] /tmp/doc-exec-159/conftest.py:10: could not import 'opt2'
You’ll see that we don’t have a opt2 module and thus the second test run of our test_func1 was skipped. A few
notes:
• the fixture functions in the conftest.py file are “session-scoped” because we don’t need to import more
than once
• if you have multiple test functions and a skipped import, you will see the [1] count increasing in the report
• you can put @pytest.mark.parametrize style parametrization on the test functions to parametrize input/output
values as well.
8.4 Working with custom markers
Here are some example using the Marking test functions with attributes mechanism.

8.4.1 Marking test functions and selecting them for a run
You can “mark” a test function with custom metadata like this:
# content of test_server.py
import pytest
@pytest.mark.webtest
def test_send_http():
pass # perform some webtest test for your app
def test_something_quick():
pass
def test_another():
pass
class TestClass:
def test_method(self):
pass
New in version 2.2.

You can then restrict a test run to only run tests marked with webtest:
$ py.test -v -m webtest
test_server.py::test_send_http PASSED
=================== 3 tests deselected by "-m 'webtest'" ===================

================== 1 passed, 3 deselected in 0.01 seconds ==================
Or the inverse, running all tests except the webtest ones:

$ py.test -v -m "not webtest"
test_server.py::test_something_quick PASSED
test_server.py::test_another PASSED
test_server.py::TestClass::test_method PASSED
================= 1 tests deselected by "-m 'not webtest'" =================

8.4.2 Selecting tests based on their node ID
You can provide one or more node IDs as positional arguments to select only specified tests. This makes it easy to
select tests based on their module, class, method, or function name:
$ py.test -v test_server.py::TestClass::test_method
8.4. Working with custom markers 123

You can also select on the class:

$ py.test -v test_server.py::TestClass
Or select multiple nodes:

$ py.test -v test_server.py::TestClass test_server.py::test_send_http
Note: Node IDs are of the form module.py::class::method or module.py::function. Node IDs
control which tests are collected, so module.py::class will select all test methods on the class. Nodes are also
created for each parameter of a parametrized fixture or test, so selecting a parametrized test must include the parameter
value, e.g. module.py::function[param].
Node IDs for failing tests are displayed in the test summary info when running py.test with the -rf option. You can
also construct Node IDs from the output of py.test --collectonly.
8.4.3 Using -k expr to select tests based on their name
You can use the -k command line option to specify an expression which implements a substring match on the test
names instead of the exact match on markers that -m provides. This makes it easy to select tests based on their names:
$ py.test -v -k http # running with the above defined example module
====================== 3 tests deselected by '-khttp' ======================

And you can also run all tests except the ones that match the keyword:

$ py.test -k "not send_http" -v

test_server.py::test_another PASSED
================= 1 tests deselected by '-knot send_http' ==================

Or to select “http” and “quick” tests:

$ py.test -k "http or quick" -v
================= 2 tests deselected by '-khttp or quick' ==================

Note: If you are using expressions such as “X and Y” then both X and Y need to be simple non-keyword names. For
example, “pass” or “from” will result in SyntaxErrors because “-k” evaluates the expression.
However, if the “-k” argument is a simple string, no such restrictions apply. Also “-k ‘not STRING”’ has no restric-
tions. You can also specify numbers like “-k 1.3” to match tests which are parametrized with the float “1.3”.
8.4.4 Registering markers
New in version 2.2.

Registering markers for your test suite is simple:
[pytest]
markers =
webtest: mark a test as a webtest.
You can ask which markers exist for your test suite - the list includes our just defined webtest markers:
$ py.test --markers
@pytest.mark.webtest: mark a test as a webtest.
@pytest.mark.skipif(condition): skip the given test function if eval(condition) results in a True val
@pytest.mark.xfail(condition, reason=None, run=True, raises=None): mark the the test function as an e
@pytest.mark.parametrize(argnames, argvalues): call a test function multiple times passing in differe
@pytest.mark.usefixtures(fixturename1, fixturename2, ...): mark tests as needing all of the specified

@pytest.mark.tryfirst: mark a hook implementation function such that the plugin machinery will try to
@pytest.mark.trylast: mark a hook implementation function such that the plugin machinery will try to
For an example on how to add and work with markers from a plugin, see Custom marker and command line option to
control test runs.
Note: It is recommended to explicitely register markers so that:

• there is one place in your test suite defining your markers
• asking for existing markers via py.test --markers gives good output
• typos in function markers are treated as an error if you use the --strict option. Future versions of pytest
are probably going to start treating non-registered markers as errors at some point.
8.4.5 Marking whole classes or modules
If you are programming with Python 2.6 or later you may use pytest.mark decorators with classes to apply markers
to all of its test methods:
# content of test_mark_classlevel.py
import pytest
@pytest.mark.webtest
class TestClass:
def test_startup(self):
pass
def test_startup_and_more(self):
pass
This is equivalent to directly applying the decorator to the two test functions.
To remain backward-compatible with Python 2.4 you can also set a pytestmark attribute on a TestClass like this:
import pytest
class TestClass:
pytestmark = pytest.mark.webtest
or if you need to use multiple markers you can use a list:

import pytest
class TestClass:
pytestmark = [pytest.mark.webtest, pytest.mark.slowtest]
You can also set a module level marker:

import pytest
pytestmark = pytest.mark.webtest
in which case it will be applied to all functions and methods defined in the module.
8.4.6 Marking individual tests when using parametrize
When using parametrize, applying a mark will make it apply to each individual test. However it is also possible to
apply a marker to an individual test instance:

import pytest
@pytest.mark.foo
@pytest.mark.parametrize(("n", "expected"), [
(1, 2),
pytest.mark.bar((1, 3)),
(2, 3),
])
def test_increment(n, expected):
assert n + 1 == expected
In this example the mark “foo” will apply to each of the three tests, whereas the “bar” mark is only applied to the
second test. Skip and xfail marks can also be applied in this way, see Skip/xfail with parametrize.
Note: If the data you are parametrizing happen to be single callables, you need to be careful when marking these
items. pytest.mark.xfail(my_func) won’t work because it’s also the signature of a function being decorated. To resolve
this ambiguity, you need to pass a reason argument: pytest.mark.xfail(func_bar, reason=”Issue#7”).
8.4.7 Custom marker and command line option to control test runs
Plugins can provide custom markers and implement specific behaviour based on it. This is a self-contained example
which adds a command line option and a parametrized test function marker to run tests specifies via named environ-
ments:
import pytest
parser.addoption("-E", action="store", metavar="NAME",
help="only run tests matching the environment NAME.")
# register an additional marker
config.addinivalue_line("markers",
"env(name): mark test to run only on named environment")
envmarker = item.get_marker("env")
if envmarker is not None:
envname = envmarker.args[0]
if envname != item.config.getoption("-E"):
pytest.skip("test requires env %r" % envname)
A test file using this local plugin:

# content of test_someenv.py
import pytest
@pytest.mark.env("stage1")
def test_basic_db_operation():
pass
and an example invocations specifying a different environment than what the test needs:
$ py.test -E stage2


collected 1 items
test_someenv.py s
======================== 1 skipped in 0.01 seconds =========================
and here is one that specifies exactly the environment needed:

$ py.test -E stage1
collected 1 items
test_someenv.py .
The --markers option always gives you a list of available markers:

$ py.test --markers
@pytest.mark.env(name): mark test to run only on named environment
@pytest.mark.skipif(condition): skip the given test function if eval(condition) results in a True val
@pytest.mark.xfail(condition, reason=None, run=True, raises=None): mark the the test function as an e
@pytest.mark.parametrize(argnames, argvalues): call a test function multiple times passing in differe
@pytest.mark.usefixtures(fixturename1, fixturename2, ...): mark tests as needing all of the specified
@pytest.mark.tryfirst: mark a hook implementation function such that the plugin machinery will try to
@pytest.mark.trylast: mark a hook implementation function such that the plugin machinery will try to
8.4.8 Reading markers which were set from multiple places
If you are heavily using markers in your test suite you may encounter the case where a marker is applied several times
to a test function. From plugin code you can read over all such settings. Example:
# content of test_mark_three_times.py
import pytest
pytestmark = pytest.mark.glob("module", x=1)
@pytest.mark.glob("class", x=2)
class TestClass:
@pytest.mark.glob("function", x=3)
def test_something(self):
pass
Here we have the marker “glob” applied three times to the same test function. From a conftest file we can read it like
this:
import sys

g = item.get_marker("glob")
if g is not None:
for info in g:
print ("glob args=%s kwargs=%s" %(info.args, info.kwargs))
sys.stdout.flush()
Let’s run this without capturing output and see what we get:
$ py.test -q -s
glob args=('function',) kwargs={'x': 3}
glob args=('class',) kwargs={'x': 2}
glob args=('module',) kwargs={'x': 1}
.
8.4.9 marking platform specific tests with pytest
Consider you have a test suite which marks tests for particular platforms, namely pytest.mark.osx,
pytest.mark.win32 etc. and you also have tests that run on all platforms and have no specific marker. If you
now want to have a way to only run the tests for your particular platform, you could use the following plugin:
#
import sys
import pytest
ALL = set("osx linux2 win32".split())
if isinstance(item, item.Function):
plat = sys.platform
if not item.get_marker(plat):
if ALL.intersection(item.keywords):
pytest.skip("cannot run on platform %s" %(plat))
then tests will be skipped if they were specified for a different platform. Let’s do a little test file to show how this looks
like:
# content of test_plat.py
import pytest
@pytest.mark.osx
def test_if_apple_is_evil():
pass
@pytest.mark.linux2
def test_if_linux_works():
pass
@pytest.mark.win32
def test_if_win32_crashes():
pass
def test_runs_everywhere():
pass

then you will see two test skipped and two executed tests as expected:
$ py.test -rs # this option reports skip reasons
collected 4 items
test_plat.py sss.
SKIP [3] /tmp/doc-exec-157/conftest.py:12: cannot run on platform linux
Note that if you specify a platform via the marker-command line option like this:
$ py.test -m linux2
collected 4 items
test_plat.py s
=================== 3 tests deselected by "-m 'linux2'" ====================

================= 1 skipped, 3 deselected in 0.01 seconds ==================
then the unmarked-tests will not be run. It is thus a way to restrict the run to the specific tests.
8.4.10 Automatically adding markers based on test names
If you a test suite where test function names indicate a certain type of test, you can implement a hook that automatically
defines markers so that you can use the -m option with it. Let’s look at this test module:
def test_interface_simple():
assert 0
def test_interface_complex():
assert 0
def test_event_simple():
assert 0
def test_something_else():
assert 0
We want to dynamically define two markers and can do it in a conftest.py plugin:

import pytest
def pytest_collection_modifyitems(items):
for item in items:
if "interface" in item.nodeid:
item.add_marker(pytest.mark.interface)
elif "event" in item.nodeid:
item.add_marker(pytest.mark.event)

We can now use the -m option to select one set:

$ py.test -m interface --tb=short
collected 4 items
test_module.py FF
================================= FAILURES =================================

__________________________ test_interface_simple ___________________________
test_module.py:3: in test_interface_simple
assert 0
E assert 0
__________________________ test_interface_complex __________________________
test_module.py:6: in test_interface_complex
assert 0
E assert 0
================== 2 tests deselected by "-m 'interface'" ==================
================== 2 failed, 2 deselected in 0.02 seconds ==================
or to select both “event” and “interface” tests:

$ py.test -m "interface or event" --tb=short
collected 4 items
test_module.py FFF
================================= FAILURES =================================

__________________________ test_interface_simple ___________________________
test_module.py:3: in test_interface_simple
assert 0
E assert 0
__________________________ test_interface_complex __________________________
test_module.py:6: in test_interface_complex
assert 0
E assert 0
____________________________ test_event_simple _____________________________
test_module.py:9: in test_event_simple
assert 0
E assert 0
============= 1 tests deselected by "-m 'interface or event'" ==============
================== 3 failed, 1 deselected in 0.02 seconds ==================
8.5 A session-fixture which can look at all collected tests
A session-scoped fixture effectively has access to all collected test items. Here is an example of a fixture function
which walks all collected tests and looks if their test class defines a callme method and calls it:
8.5. A session-fixture which can look at all collected tests 131

import pytest
@pytest.fixture(scope="session", autouse=True)
def callattr_ahead_of_alltests(request):
print ("callattr_ahead_of_alltests called")
seen = set([None])
session = request.node
for item in session.items:
cls = item.getparent(pytest.Class)
if cls not in seen:
if hasattr(cls.obj, "callme"):
cls.obj.callme()
seen.add(cls)
test classes may now define a callme method which will be called ahead of running any tests:
class TestHello:
@classmethod
def callme(cls):
print ("callme called!")
print ("test_method1 called")
print ("test_method1 called")
class TestOther:
@classmethod
def callme(cls):
print ("callme other called")
def test_other(self):
print ("test other")
# works with unittest as well ...

import unittest
class SomeTest(unittest.TestCase):
@classmethod
def callme(self):
print ("SomeTest callme called")
def test_unit1(self):
print ("test_unit1 method called")
If you run this without output capturing:

$ py.test -q -s test_module.py
callattr_ahead_of_alltests called
callme called!
callme other called
SomeTest callme called
test_method1 called
.test_method1 called
.test other
.test_unit1 method called
.

8.6 Changing standard (Python) test discovery
8.6.1 Changing directory recursion
You can set the norecursedirs option in an ini-file, for example your setup.cfg in the project root directory:
[pytest]
norecursedirs = .svn _build tmp*
This would tell pytest to not recurse into typical subversion or sphinx-build directories or into any tmp prefixed
directory.
8.6.2 Changing naming conventions
You can configure different naming conventions by setting the python_files, python_classes and
python_functions configuration options. Example:
# can also be defined in in tox.ini or pytest.ini file
[pytest]
python_files=check_*.py
python_classes=Check
python_functions=*_check
This would make pytest look for tests in files that match the check_* .py glob-pattern, Check prefixes in
classes, and functions and methods that match *_check. For example, if we have:
# content of check_myapp.py
class CheckMyApp:
def simple_check(self):
pass
def complex_check(self):
pass
then the test collection looks like this:

rootdir: /tmp/doc-exec-160, inifile: setup.cfg
collected 2 items
<Module 'check_myapp.py'>
<Class 'CheckMyApp'>
<Instance '()'>
<Function 'simple_check'>
<Function 'complex_check'>
============================= in 0.01 seconds =============================
Note: the python_functions and python_classes options has no effect for unittest.TestCase test
discovery because pytest delegates detection of test case methods to unittest code.
8.6. Changing standard (Python) test discovery 133

8.6.3 Interpreting cmdline arguments as Python packages
You can use the --pyargs option to make pytest try interpreting arguments as python package names, deriving
their file system path and then running the test. For example if you have unittest2 installed you can type:
py.test --pyargs unittest2.test.test_skipping -q
which would run the respective test module. Like with other options, through an ini-file and the addopts option you
can make this change more permanently:
[pytest]
addopts = --pyargs
Now a simple invocation of py.test NAME will check if NAME exists as an importable package/module and
otherwise treat it as a filesystem path.
8.6.4 Finding out what is collected
You can always peek at the collection tree without running tests like this:
. $ py.test --collect-only pythoncollection.py
collected 3 items
<Module 'example/pythoncollection.py'>
<Function 'test_function'>
<Class 'TestClass'>
<Instance '()'>
<Function 'test_method'>
<Function 'test_anothermethod'>
============================= in 0.01 seconds =============================
8.6.5 customizing test collection to find all .py files
You can easily instruct pytest to discover tests from every python file:
[pytest]
python_files = *.py
However, many projects will have a setup.py which they don’t want to be imported. Moreover, there may files only
importable by a specific python version. For such cases you can dynamically define files to be ignored by listing them
in a conftest.py file:
import sys
collect_ignore = ["setup.py"]
if sys.version_info[0] > 2:
collect_ignore.append("pkg/module_py2.py")
And then if you have a module file like this:

# content of pkg/module_py2.py
def test_only_on_python2():
try:
assert 0
except Exception, e:
pass
and a setup.py dummy file like this:

# content of setup.py
0/0 # will raise exeption if imported
then a pytest run on python2 will find the one test when run with a python2 interpreters and will leave out the setup.py
file:
rootdir: /tmp/doc-exec-160, inifile: pytest.ini
collected 0 items
============================= in 0.01 seconds =============================
If you run with a Python3 interpreter the moduled added through the conftest.py file will not be considered for test
collection.
8.7 Working with non-python tests
8.7.1 A basic example for specifying tests in Yaml files
Here is an example conftest.py (extracted from Ali Afshnars special purpose pytest-yamlwsgi plugin). This
conftest.py will collect test*.yml files and will execute the yaml-formatted content as custom tests:
import pytest
def pytest_collect_file(parent, path):

if path.ext == ".yml" and path.basename.startswith("test"):
return YamlFile(path, parent)
class YamlFile(pytest.File):
def collect(self):
import yaml # we need a yaml parser, e.g. PyYAML
raw = yaml.safe_load(self.fspath.open())
for name, spec in raw.items():
yield YamlItem(name, self, spec)
class YamlItem(pytest.Item):
def __init__(self, name, parent, spec):
super(YamlItem, self).__init__(name, parent)
self.spec = spec
def runtest(self):
for name, value in self.spec.items():
# some custom test execution (dumb example follows)
8.7. Working with non-python tests 135

if name != value:
raise YamlException(self, name, value)
def repr_failure(self, excinfo):

""" called when self.runtest() raises an exception. """
if isinstance(excinfo.value, YamlException):
return "\n".join([
"usecase execution failed",
" spec failed: %r: %r" % excinfo.value.args[1:3],
" no further details known at this point."
])
def reportinfo(self):
return self.fspath, 0, "usecase: %s" % self.name
class YamlException(Exception):
""" custom exception for error reporting. """
You can create a simple example file:

# test_simple.yml
ok:
sub1: sub1
hello:
world: world
some: other
and if you installed PyYAML or a compatible YAML-parser you can now execute the test specification:
nonpython $ py.test test_simple.yml
collected 2 items
test_simple.yml .F
================================= FAILURES =================================

______________________________ usecase: hello ______________________________
usecase execution failed
spec failed: 'some': 'other'
no further details known at this point.
You get one dot for the passing sub1: sub1 check and one failure. Obviously in the above conftest.py you’ll
want to implement a more interesting interpretation of the yaml-values. You can easily write your own domain specific
testing language this way.
Note: repr_failure(excinfo) is called for representing test failures. If you create custom collection nodes
you can return an error representation string of your choice. It will be reported as a (red) string.
reportinfo() is used for representing the test location and is also consulted when reporting in verbose mode:
nonpython $ py.test -v

test_simple.yml::ok PASSED
test_simple.yml::hello FAILED
================================= FAILURES =================================

______________________________ usecase: hello ______________________________
usecase execution failed
spec failed: 'some': 'other'
no further details known at this point.
While developing your custom test collection and execution it’s also interesting to just look at the collection tree:
nonpython $ py.test --collect-only
collected 2 items
<YamlFile 'example/nonpython/test_simple.yml'>
<YamlItem 'ok'>
<YamlItem 'hello'>
============================= in 0.04 seconds =============================
8.7. Working with non-python tests 137


CHAPTER
NINE
TALKS AND TUTORIALS
Next Open Trainings

professional testing with pytest and tox, 24-26th November 2014, Freiburg, Germany
9.1 Talks and blog postings
• Introduction to pytest, Andreas Pelme, EuroPython 2014.

• Advanced Uses of py.test Fixtures, Floris Bruynooghe, EuroPython 2014.
• Why i use py.test and maybe you should too, Andy Todd, Pycon AU 2013
• 3-part blog series about pytest from @pydanny alias Daniel Greenfeld (January 2014)
• pytest: helps you write better Django apps, Andreas Pelme, DjangoCon Europe 2014.
• pytest fixtures: explicit, modular, scalable
• Testing Django Applications with pytest, Andreas Pelme, EuroPython 2013.
• Testes pythonics com py.test, Vinicius Belchior Assef Neto, Plone Conf 2013, Brazil.
• Introduction to py.test fixtures, FOSDEM 2013, Floris Bruynooghe.
• pytest feature and release highlights, Holger Krekel (GERMAN, October 2013)
• pytest introduction from Brian Okken (January 2013)
• monkey patching done right (blog post, consult monkeypatch plugin for up-to-date API)
Test parametrization:
• generating parametrized tests with funcargs (uses deprecated addcall() API.
• test generators and cached setup
• parametrizing tests, generalized (blog post)
• putting test-hooks into local or global plugins (blog post)
Assertion introspection:
• (07/2011) Behind the scenes of pytest’s new assertion rewriting
Distributed testing:
• simultaneously test your code on all platforms (blog entry)
139
Plugin specific examples:

• skipping slow tests by default in pytest (blog entry)
• many examples in the docs for plugins
9.2 Older conference talks and tutorials
• pycon australia 2012 pytest talk from Brianna Laugher (video, slides, code)
• pycon 2012 US talk video from Holger Krekel
• pycon 2010 tutorial PDF and tutorial1 repository
• ep2009-rapidtesting.pdf tutorial slides (July 2009):
– testing terminology
– basic pytest usage, file system layout
– test function arguments (funcargs) and test fixtures
– existing plugins
– distributed testing
• ep2009-pytest.pdf 60 minute pytest talk, highlighting unique features and a roadmap (July 2009)
• pycon2009-pytest-introduction.zip slides and files, extended version of pytest basic introduction, discusses more
options, also introduces old-style xUnit setup, looponfailing and other features.
• pycon2009-pytest-advanced.pdf contain a slightly older version of funcargs and distributed testing, compared to
the EuroPython 2009 slides.
140 Chapter 9. Talks and Tutorials

CHAPTER
TEN
CONTRIBUTION GETTING STARTED
Contributions are highly welcomed and appreciated. Every little help counts, so do not hesitate!
Contribution links
• Contribution getting started
– Submit a plugin, co-develop pytest
– Report bugs
– Submit feedback for developers
– Fix bugs
– Implement features
– Write documentation
– Preparing Pull Requests on Bitbucket
– Using git with bitbucket/hg
10.1 Submit a plugin, co-develop pytest
Pytest development of the core, some plugins and support code happens in repositories living under:
• the pytest-dev bitbucket team
• the pytest-dev github organisation
All pytest-dev team members have write access to all contained repositories. pytest core and plugins are generally
developed using pull requests to respective repositories.
You can submit your plugin by subscribing to the pytest-dev mail list and writing a mail pointing to your existing
pytest plugin repository which must have the following:
• PyPI presence with a setup.py that contains a license, pytest- prefixed, version number, authors, short
and long description.
• a tox.ini for running tests using tox.
• a README.txt describing how to use the plugin and on which platforms it runs.
• a LICENSE.txt file or equivalent containing the licensing information, with matching info in setup.py.
• an issue tracker unless you rather want to use the core pytest issue tracker.
If no contributor strongly objects and two agree, the repo will be transferred to the pytest-dev organisation and
you’ll become a member of the pytest-dev team, with commit rights to all projects. We recommend that each
plugin has at least three people who have the right to release to pypi.
141
10.2 Report bugs
Report bugs for pytest at https://bitbucket.org/pytest-dev/pytest/issues

If you are reporting a bug, please include:
• Your operating system name and version.
• Any details about your local setup that might be helpful in troubleshooting, specifically Python interpreter
version, installed libraries and pytest version.
• Detailed steps to reproduce the bug.
10.3 Submit feedback for developers
Do you like pytest? Share some love on Twitter or in your blog posts!
We’d also like to hear about your propositions and suggestions. Feel free to submit them as issues and:
• Set the “kind” to “enhancement” or “proposal” so that we can quickly find about them.
• Explain in detail how they should work.
• Keep the scope as narrow as possible. This will make it easier to implement.
• If you have required skills and/or knowledge, we are very happy for pull requests.
10.4 Fix bugs
Look through the BitBucket issues for bugs. Here is sample filter you can use: https://bitbucket.org/pytest-
dev/pytest/issues?status=new&status=open&kind=bug
Talk to developers to find out how you can fix specific bugs.
10.5 Implement features
Look through the BitBucket issues for enhancements. Here is sample filter you can use: https://bitbucket.org/pytest-
dev/pytest/issues?status=new&status=open&kind=enhancement
Talk to developers to find out how you can implement specific features.
10.6 Write documentation
pytest could always use more documentation. What exactly is needed?

• More complementary documentation. Have you perhaps found something unclear?
• Documentation translations. We currently have English and Japanese versions.
• Docstrings. There’s never too much of them.
• Blog posts, articles and such – they’re all very appreciated.
142 Chapter 10. Contribution getting started

10.7 Preparing Pull Requests on Bitbucket
Note: What is a “pull request”? It informs project’s core developers about the changes you want to review and merge.
Pull requests are stored on BitBucket servers. Once you send pull request, we can discuss it’s potential modifications
and even add more commits to it later on.
The primary development platform for pytest is BitBucket. You can find all the issues there and submit your pull
requests.
1. Fork the pytest BitBucket repository. It’s fine to use pytest as your fork repository name because it will live
under your user.
2. Clone your fork locally using Mercurial (hg) and create a branch:
$ hg clone ssh://hg@bitbucket.org/YOUR_BITBUCKET_USERNAME/pytest
$ cd pytest
$ hg up pytest-2.7 # if you want to fix a bug for the pytest-2.7 series
$ hg up default # if you want to add a feature bound for the next minor release
$ hg branch your-branch-name # your feature/bugfix branch
If you need some help with Mercurial, follow this quick start guide:
http://mercurial.selenic.com/wiki/QuickStart
3. Create a development environment (will implicitly use http://www.virtualenv.org/en/latest/):
$ make develop
$ source .env/bin/activate
4. You can now edit your local working copy.

You need to have Python 2.7 and 3.4 available in your system. Now running tests is as simple as issuing this
command:
$ python runtox.py -e py27,py34,flakes
This command will run tests via the “tox” tool against Python 2.7 and 3.4 and also perform “flakes” coding-style
checks. runtox.py is a thin wrapper around tox which installs from a development package index where
newer (not yet released to pypi) versions of dependencies (especially py) might be present.
To run tests on py27 and pass options (e.g. enter pdb on failure) to pytest you can do:
$ python runtox.py -e py27 -- --pdb
or to only run tests in a particular test module on py34:

$ python runtox.py -e py34 -- testing/test_config.py
5. Commit and push once your tests pass and you are happy with your change(s):
$ hg commit -m"<commit message>"
$ hg push -b .
6. Finally, submit a pull request through the BitBucket website:
10.7. Preparing Pull Requests on Bitbucket 143

source: YOUR_BITBUCKET_USERNAME/pytest
branch: your-branch-name
target: pytest-dev/pytest
branch: default # if it's a feature
branch: pytest-VERSION # if it's a bugfix
10.8 Using git with bitbucket/hg
There used to be the pytest GitHub mirror. It was removed in favor of the Mercurial one, to remove confusion of
people not knowing where it’s better to put their issues and pull requests. Also it wasn’t easily possible to automate
the mirroring process.
In general we recommend to work with the same version control system of the original repository. If you insist on
using git with bitbucket/hg you may try gitifyhg but are on your own and need to submit pull requests through the
respective platform, nevertheless.
144 Chapter 10. Contribution getting started

CHAPTER
ELEVEN
PYTEST-2.3: REASONING FOR FIXTURE/FUNCARG EVOLUTION
Target audience: Reading this document requires basic knowledge of python testing, xUnit setup methods and the
(previous) basic pytest funcarg mechanism, see http://pytest.org/2.2.4/funcargs.html If you are new to pytest, then you
can simply ignore this section and read the other sections.
11.1 Shortcomings of the previous pytest_funcarg__ mechanism
The pre pytest-2.3 funcarg mechanism calls a factory each time a funcarg for a test function is required. If a factory
wants to re-use a resource across different scopes, it often used the request.cached_setup() helper to manage
caching of resources. Here is a basic example how we could implement a per-session Database object:
class Database:
def __init__(self):
print ("database instance created")
def destroy(self):
print ("database instance destroyed")
def pytest_funcarg__db(request):
return request.cached_setup(setup=DataBase,
teardown=lambda db: db.destroy,
scope="session")
There are several limitations and difficulties with this approach:

1. Scoping funcarg resource creation is not straight forward, instead one must understand the intricate
cached_setup() method mechanics.
2. parametrizing the “db” resource is not straight forward: you need to apply a “parametrize” decorator or imple-
ment a pytest_generate_tests() hook calling parametrize() which performs parametrization at
the places where the resource is used. Moreover, you need to modify the factory to use an extrakey parameter
containing request.param to the cached_setup() call.
3. Multiple parametrized session-scoped resources will be active at the same time, making it hard for them to affect
global state of the application under test.
4. there is no way how you can make use of funcarg factories in xUnit setup methods.
5. A non-parametrized fixture function cannot use a parametrized funcarg resource if it isn’t stated in the test
function signature.
All of these limitations are addressed with pytest-2.3 and its improved fixture mechanism.
145
11.2 Direct scoping of fixture/funcarg factories
Instead of calling cached_setup() with a cache scope, you can use the @pytest.fixture decorator and directly state the
scope:
def db(request):
# factory will only be invoked once per session -
db = DataBase()
request.addfinalizer(db.destroy) # destroy when session is finished
return db
This factory implementation does not need to call cached_setup() anymore because it will only be invoked once
per session. Moreover, the request.addfinalizer() registers a finalizer according to the specified resource
scope on which the factory function is operating.
11.3 Direct parametrization of funcarg resource factories
Previously, funcarg factories could not directly cause parametrization. You needed to specify a @parametrize
decorator on your test function or implement a pytest_generate_tests hook to perform parametrization, i.e.
calling a test multiple times with different value sets. pytest-2.3 introduces a decorator for use on the factory itself:
@pytest.fixture(params=["mysql", "pg"])
def db(request):
... # use request.param
Here the factory will be invoked twice (with the respective “mysql” and “pg” values set as request.param at-
tributes) and and all of the tests requiring “db” will run twice as well. The “mysql” and “pg” values will also be used
for reporting the test-invocation variants.
This new way of parametrizing funcarg factories should in many cases allow to re-use already written facto-
ries because effectively request.param was already used when test functions/classes were parametrized via
parametrize(indirect=True)() calls.
Of course it’s perfectly fine to combine parametrization and scoping:
@pytest.fixture(scope="session", params=["mysql", "pg"])
def db(request):
if request.param == "mysql":
db = MySQL()
elif request.param == "pg":
db = PG()
request.addfinalizer(db.destroy) # destroy when session is finished
return db
This would execute all tests requiring the per-session “db” resource twice, receiving the values created by the two
respective invocations to the factory function.
11.4 No pytest_funcarg__ prefix when using @fixture decorator
When using the @fixture decorator the name of the function denotes the name under which the resource can be
accessed as a function argument:
146 Chapter 11. pytest-2.3: reasoning for fixture/funcarg evolution

@pytest.fixture()
def db(request):
...
The name under which the funcarg resource can be requested is db.
You can still use the “old” non-decorator way of specifying funcarg factories aka:
def pytest_funcarg__db(request):
...
But it is then not possible to define scoping and parametrization. It is thus recommended to use the factory decorator.
11.5 solving per-session setup / autouse fixtures
pytest for a long time offered a pytest_configure and a pytest_sessionstart hook which are often used to setup global
resources. This suffers from several problems:
1. in distributed testing the master process would setup test resources that are never needed because it only co-
ordinates the test run activities of the slave processes.
2. if you only perform a collection (with “–collect-only”) resource-setup will still be executed.
3. If a pytest_sessionstart is contained in some subdirectories conftest.py file, it will not be called. This stems
from the fact that this hook is actually used for reporting, in particular the test-header with platform/custom
information.
Moreover, it was not easy to define a scoped setup from plugins or conftest files other than to implement a
pytest_runtest_setup() hook and caring for scoping/caching yourself. And it’s virtually impossible to do
this with parametrization as pytest_runtest_setup() is called during test execution and parametrization hap-
pens at collection time.
It follows that pytest_configure/session/runtest_setup are often not appropriate for implementing common fixture
needs. Therefore, pytest-2.3 introduces autouse fixtures (xUnit setup on steroids) which fully integrate with the generic
fixture mechanism and obsolete many prior uses of pytest hooks.
11.6 funcargs/fixture discovery now happens at collection time
pytest-2.3 takes care to discover fixture/funcarg factories at collection time. This is more efficient especially for large
test suites. Moreover, a call to “py.test –collect-only” should be able to in the future show a lot of setup-information
and thus presents a nice method to get an overview of fixture management in your project.
11.7 Conclusion and compatibility notes
funcargs were originally introduced to pytest-2.0. In pytest-2.3 the mechanism was extended and refined and is now
described as fixtures:
• previously funcarg factories were specified with a special pytest_funcarg__NAME prefix instead of using
the @pytest.fixture decorator.
• Factories received a request object which managed caching through request.cached_setup() calls
and allowed using other funcargs via request.getfuncargvalue() calls. These intricate APIs made it
hard to do proper parametrization and implement resource caching. The new pytest.fixture‘() decorator
allows to declare the scope and let pytest figure things out for you.
11.5. solving per-session setup / autouse fixtures 147

• if you used parametrization and funcarg factories which made use of request.cached_setup() it is
recommeneded to invest a few minutes and simplify your fixture function code to use the Fixtures as Function
arguments decorator instead. This will also allow to take advantage of the automatic per-resource grouping of
tests.
148 Chapter 11. pytest-2.3: reasoning for fixture/funcarg evolution

CHAPTER
TWELVE
RELEASE ANNOUNCEMENTS
12.1 pytest-2.7.1: bug fixes
pytest is a mature Python testing tool with more than a 1100 tests against itself, passing on many different interpreters
and platforms. This release is supposed to be drop-in compatible to 2.7.0.
See below for the changes and see docs at:
http://pytest.org
As usual, you can upgrade from pypi via:
pip install -U pytest
Thanks to all who contributed to this release, among them:

Bruno Oliveira Holger Krekel Ionel Maries Cristian Floris Bruynooghe
Happy testing, The py.test Development Team
12.1.1 2.7.1 (compared to 2.7.0)
• fix issue731: do not get confused by the braces which may be present and unbalanced in an object’s repr while
collapsing False explanations. Thanks Carl Meyer for the report and test case.
• fix issue553: properly handling inspect.getsourcelines failures in FixtureLookupError which would lead to to an
internal error, obfuscating the original problem. Thanks talljosh for initial diagnose/patch and Bruno Oliveira
for final patch.
• fix issue660: properly report scope-mismatch-access errors independently from ordering of fixture arguments.
Also avoid the pytest internal traceback which does not provide information to the user. Thanks Holger Krekel.
• streamlined and documented release process. Also all versions (in setup.py and documentation generation) are
now read from _pytest/__init__.py. Thanks Holger Krekel.
• fixed docs to remove the notion that yield-fixtures are experimental. They are here to stay :) Thanks Bruno
Oliveira.
• Support building wheels by using environment markers for the requirements. Thanks Ionel Maries Cristian.
• fixed regression to 2.6.4 which surfaced e.g. in lost stdout capture printing when tests raised SystemExit. Thanks
Holger Krekel.
• reintroduced _pytest fixture of the pytester plugin which is used at least by pytest-xdist.
149
12.2 pytest-2.7.0: fixes, features, speed improvements
and platforms. This release is supposed to be drop-in compatible to 2.6.X.
See below for the changes and see docs at:
http://pytest.org
Thanks to all who contributed, among them:

Anatoly Bubenkoff Floris Bruynooghe Brianna Laugher Eric Siegerman Daniel Hahler Charles Cloud
Tom Viner Holger Peters Ldiary Translations almarklein
have fun, holger krekel
12.2.1 2.7.0 (compared to 2.6.4)
• fix issue435: make reload() work when assert rewriting is active. Thanks Daniel Hahler.
• fix issue616: conftest.py files and their contained fixutres are now properly considered for visibility, indepen-
dently from the exact current working directory and test arguments that are used. Many thanks to Eric Siegerman
and his PR235 which contains systematic tests for conftest visibility and now passes. This change also intro-
duces the concept of a rootdir which is printed as a new pytest header and documented in the pytest customize
web page.
• change reporting of “diverted” tests, i.e. tests that are collected in one file but actually come from another (e.g.
when tests in a test class come from a base class in a different file). We now show the nodeid and indicate via a
postfix the other file.
• add ability to set command line options by environment variable PYTEST_ADDOPTS.
• added documentation on the new pytest-dev teams on bitbucket and github. See
https://pytest.org/latest/contributing.html . Thanks to Anatoly for pushing and initial work on this.
• fix issue650: new option --docttest-ignore-import-errors which will turn import errors in doctests
into skips. Thanks Charles Cloud for the complete PR.
• fix issue655: work around different ways that cause python2/3 to leak sys.exc_info into fixtures/tests causing
failures in 3rd party code
• fix issue615: assertion re-writing did not correctly escape % signs when formatting boolean operations, which
tripped over mixing booleans with modulo operators. Thanks to Tom Viner for the report, triaging and fix.
• implement issue351: add ability to specify parametrize ids as a callable to generate custom test ids. Thanks
Brianna Laugher for the idea and implementation.
• introduce and document new hookwrapper mechanism useful for plugins which want to wrap the execution
of certain hooks for their purposes. This supersedes the undocumented __multicall__ protocol which
pytest itself and some external plugins use. Note that pytest-2.8 is scheduled to drop supporting the old
__multicall__ and only support the hookwrapper protocol.
• majorly speed up invocation of plugin hooks
• use hookwrapper mechanism in builtin pytest plugins.
• add a doctest ini option for doctest flags, thanks Holger Peters.
150 Chapter 12. Release announcements

• add note to docs that if you want to mark a parameter and the parameter is a callable, you also need to pass in a
reason to disambiguate it from the “decorator” case. Thanks Tom Viner.
• “python_classes” and “python_functions” options now support glob-patterns for test discovery, as discussed in
issue600. Thanks Ldiary Translations.
• allow to override parametrized fixtures with non-parametrized ones and vice versa (bubenkoff).
• fix issue463: raise specific error for ‘parameterize’ misspelling (pfctdayelise).
• On failure, the sys.last_value, sys.last_type and sys.last_traceback are set, so that a user
can inspect the error via postmortem debugging (almarklein).
12.3 pytest-2.6.3: fixes and little improvements
and platforms. This release is drop-in compatible to 2.5.2 and 2.6.X. See below for the changes and see docs at:
http://pytest.org

Floris Bruynooghe Oleg Sinyavskiy Uwe Schmitt Charles Cloud Wolfgang Schnerring
12.4 Changes 2.6.3
• fix issue575: xunit-xml was reporting collection errors as failures instead of errors, thanks Oleg Sinyavskiy.
• fix issue582: fix setuptools example, thanks Laszlo Papp and Ronny Pfannschmidt.
• Fix infinite recursion bug when pickling capture.EncodedFile, thanks Uwe Schmitt.
• fix issue589: fix bad interaction with numpy and others when showing exceptions. Check for precise “maximum
recursion depth exceed” exception instead of presuming any RuntimeError is that one (implemented in py dep).
Thanks Charles Cloud for analysing the issue.
• fix conftest related fixture visibility issue: when running with a CWD outside a test package pytest would get
fixture discovery wrong. Thanks to Wolfgang Schnerring for figuring out a reproducable example.
• Introduce pytest_enter_pdb hook (needed e.g. by pytest_timeout to cancel the timeout when interactively enter-
ing pdb). Thanks Wolfgang Schnerring.
• check xfail/skip also with non-python function test items. Thanks Floris Bruynooghe.
12.5 pytest-2.6.2: few fixes and cx_freeze support
and platforms. This release is drop-in compatible to 2.5.2 and 2.6.X. It also brings support for including pytest with
cx_freeze or similar freezing tools into your single-file app distribution. For details see the CHANGELOG below.
See docs at:
12.3. pytest-2.6.3: fixes and little improvements 151

http://pytest.org

Floris Bruynooghe Benjamin Peterson Bruno Oliveira
12.5.1 2.6.2
• Added function pytest.freeze_includes(), which makes it easy to embed pytest into executables using tools like
cx_freeze. See docs for examples and rationale. Thanks Bruno Oliveira.
• Improve assertion rewriting cache invalidation precision.
• fixed issue561: adapt autouse fixture example for python3.
• fixed issue453: assertion rewriting issue with __repr__ containing “n{”, “n}” and “n~”.
• fix issue560: correctly display code if an “else:” or “finally:” is followed by statements on the same line.
• Fix example in monkeypatch documentation, thanks t-8ch.
• fix issue572: correct tmpdir doc example for python3.
• Do not mark as universal wheel because Python 2.6 is different from other builds due to the extra argparse
dependency. Fixes issue566. Thanks sontek.
12.6 pytest-2.6.1: fixes and new xfail feature
pytest is a mature Python testing tool with more than a 1100 tests against itself, passing on many different inter-
preters and platforms. The 2.6.1 release is drop-in compatible to 2.5.2 and actually fixes some regressions introduced
with 2.6.0. It also brings a little feature to the xfail marker which now recognizes expected exceptions, see the
CHANGELOG below.
See docs at:
http://pytest.org

Floris Bruynooghe Bruno Oliveira Nicolas Delaby
12.7 Changes 2.6.1
• No longer show line numbers in the –verbose output, the output is now purely the nodeid. The line number is
still shown in failure reports. Thanks Floris Bruynooghe.

• fix issue437 where assertion rewriting could cause pytest-xdist slaves to collect different tests. Thanks Bruno
Oliveira.
• fix issue555: add “errors” attribute to capture-streams to satisfy some distutils and possibly other code accessing
sys.stdout.errors.
• fix issue547 capsys/capfd also work when output capturing (“-s”) is disabled.
• address issue170: allow pytest.mark.xfail(...) to specify expected exceptions via an optional “raises=EXC”
argument where EXC can be a single exception or a tuple of exception classes. Thanks David Mohr for the
complete PR.
• fix integration of pytest with unittest.mock.patch decorator when it uses the “new” argument. Thanks Nicolas
Delaby for test and PR.
• fix issue with detecting conftest files if the arguments contain ”::” node id specifications (copy pasted from “-v”
output)
• fix issue544 by only removing “@NUM” at the end of ”::” separated parts and if the part has an ”.py” extension
• don’t use py.std import helper, rather import things directly. Thanks Bruno Oliveira.
12.8 pytest-2.6.0: shorter tracebacks, new warning system, test run-

ner compat
and platforms.
The 2.6.0 release should be drop-in backward compatible to 2.5.2 and fixes a number of bugs and brings some new
features, mainly:
• shorter tracebacks by default: only the first (test function) entry and the last (failure location) entry are shown,
the ones between only in “short” format. Use --tb=long to get back the old behaviour of showing “long”
entries everywhere.
• a new warning system which reports oddities during collection and execution. For example, ignoring collecting
Test* classes with an __init__ now produces a warning.
• various improvements to nose/mock/unittest integration
Note also that 2.6.0 departs with the “zero reported bugs” policy because it has been too hard to keep up with it,
unfortunately. Instead we are for now rather bound to work on “upvoted” issues in the https://bitbucket.org/pytest-
dev/pytest/issues?status=new&status=open&sort=-votes issue tracker.
See docs at:
http://pytest.org

Benjamin Peterson Jurko Gospodnetić Floris Bruynooghe Marc Abramowitz Marc Schlaich Trevor Beko-
lay Bruno Oliveira Alex Groenholm
12.8. pytest-2.6.0: shorter tracebacks, new warning system, test runner compat 153
12.8.1 2.6.0
• fix issue537: Avoid importing old assertion reinterpretation code by default. Thanks Benjamin Peterson.
• fix issue364: shorten and enhance tracebacks representation by default. The new “–tb=auto” option (default)
will only display long tracebacks for the first and last entry. You can get the old behaviour of printing all entries
as long entries with “–tb=long”. Also short entries by default are now printed very similarly to “–tb=native”
ones.
• fix issue514: teach assertion reinterpretation about private class attributes Thanks Benjamin Peterson.
• change -v output to include full node IDs of tests. Users can copy a node ID from a test run, including line
number, and use it as a positional argument in order to run only a single test.
• fix issue 475: fail early and comprehensible if calling pytest.raises with wrong exception type.
• fix issue516: tell in getting-started about current dependencies.
• cleanup setup.py a bit and specify supported versions. Thanks Jurko Gospodnetic for the PR.
• change XPASS colour to yellow rather then red when tests are run with -v.
• fix issue473: work around mock putting an unbound method into a class dict when double-patching.
• fix issue498: if a fixture finalizer fails, make sure that the fixture is still invalidated.
• fix issue453: the result of the pytest_assertrepr_compare hook now gets it’s newlines escaped so that for-
mat_exception does not blow up.
• internal new warning system: pytest will now produce warnings when it detects oddities in your test collection or
execution. Warnings are ultimately sent to a new pytest_logwarning hook which is currently only implemented
by the terminal plugin which displays warnings in the summary line and shows more details when -rw (report
on warnings) is specified.
• change skips into warnings for test classes with an __init__ and callables in test modules which look like a test
but are not functions.
• fix issue436: improved finding of initial conftest files from command line arguments by using the result of
parse_known_args rather than the previous flaky heuristics. Thanks Marc Abramowitz for tests and initial fixing
approaches in this area.
• fix issue #479: properly handle nose/unittest(2) SkipTest exceptions during collection/loading of test modules.
Thanks to Marc Schlaich for the complete PR.
• fix issue490: include pytest_load_initial_conftests in documentation and improve docstring.
• fix issue472: clarify that pytest.config.getvalue() cannot work if it’s triggered ahead of command
line parsing.
• merge PR123: improved integration with mock.patch decorator on tests.
• fix issue412: messing with stdout/stderr FD-level streams is now captured without crashes.
• fix issue483: trial/py33 works now properly. Thanks Daniel Grana for PR.
• improve example for pytest integration with “python setup.py test” which now has a generic “-a” or “–pytest-
args” option where you can pass additional options as a quoted string. Thanks Trevor Bekolay.
• simplified internal capturing mechanism and made it more robust against tests or setups changing FD1/FD2,
also better integrated now with pytest.pdb() in single tests.
• improvements to pytest’s own test-suite leakage detection, courtesy of PRs from Marc Abramowitz
• fix issue492: avoid leak in test_writeorg. Thanks Marc Abramowitz.
• fix issue493: don’t run tests in doc directory with python setup.py test (use tox -e doctesting for that)

• fix issue486: better reporting and handling of early conftest loading failures
• some cleanup and simplification of internal conftest handling.
• work a bit harder to break reference cycles when catching exceptions. Thanks Jurko Gospodnetic.
• fix issue443: fix skip examples to use proper comparison. Thanks Alex Groenholm.
• support nose-style __test__ attribute on modules, classes and functions, including unittest-style Classes. If
set to False, the test will not be collected.
• fix issue512: show “<notset>” for arguments which might not be set in monkeypatch plugin. Improves output
in documentation.
• avoid importing “py.test” (an old alias module for “pytest”)
12.9 pytest-2.5.2: fixes
and platforms.
The 2.5.2 release fixes a few bugs with two maybe-bugs remaining and actively being worked on (and waiting for the
bug reporter’s input). We also have a new contribution guide thanks to Piotr Banaszkiewicz and others.
See docs at:
http://pytest.org
Thanks to the following people who contributed to this release:

Anatoly Bubenkov Ronny Pfannschmidt Floris Bruynooghe Bruno Oliveira Andreas Pelme Jurko
Gospodnetić Piotr Banaszkiewicz Simon Liedtke lakka Lukasz Balcerzak Philippe Muller Daniel Hahler
12.9.1 2.5.2
• fix issue409 – better interoperate with cx_freeze by not trying to import from collections.abc which causes
problems for py27/cx_freeze. Thanks Wolfgang L. for reporting and tracking it down.
• fixed docs and code to use “pytest” instead of “py.test” almost everywhere. Thanks Jurko Gospodnetic for the
complete PR.
• fix issue425: mention at end of “py.test -h” that –markers and –fixtures work according to specified test path (or
current dir)
• fix issue413: exceptions with unicode attributes are now printed correctly also on python2 and with pytest-xdist
runs. (the fix requires py-1.4.20)
• copy, cleanup and integrate py.io capture from pylib 1.4.20.dev2 (rev 13d9af95547e)
• address issue416: clarify docs as to conftest.py loading semantics
• fix issue429: comparing byte strings with non-ascii chars in assert expressions now work better. Thanks Floris
Bruynooghe.
• make capfd/capsys.capture private, its unused and shouldnt be exposed
12.9. pytest-2.5.2: fixes 155

12.10 pytest-2.5.1: fixes and new home page styling
and platforms.
The 2.5.1 release maintains the “zero-reported-bugs” promise by fixing the three bugs reported since the last release a
few days ago. It also features a new home page styling implemented by Tobias Bieniek, based on the flask theme from
Armin Ronacher:
http://pytest.org
If you have anything more to improve styling and docs, we’d be very happy to merge further pull requests.
On the coding side, the release also contains a little enhancement to fixture decorators allowing to directly influence
generation of test ids, thanks to Floris Bruynooghe. Other thanks for helping with this release go to Anatoly Bubenkoff
and Ronny Pfannschmidt.
have fun and a nice remaining “bug-free” time of the year :) holger krekel
12.10.1 2.5.1
• merge new documentation styling PR from Tobias Bieniek.

• fix issue403: allow parametrize of multiple same-name functions within a collection node. Thanks Andreas
Kloeckner and Alex Gaynor for reporting and analysis.
• Allow parameterized fixtures to specify the ID of the parameters by adding an ids argument to pytest.fixture()
and pytest.yield_fixture(). Thanks Floris Bruynooghe.
• fix issue404 by always using the binary xml escape in the junitxml plugin. Thanks Ronny Pfannschmidt.
• fix issue407: fix addoption docstring to point to argparse instead of optparse. Thanks Daniel D. Wright.
12.11 pytest-2.5.0: now down to ZERO reported bugs!
pytest-2.5.0 is a big fixing release, the result of two community bug fixing days plus numerous additional works from
many people and reporters. The release should be fully compatible to 2.4.2, existing plugins and test suites. We aim at
maintaining this level of ZERO reported bugs because it’s no fun if your testing tool has bugs, is it? Under a condition,
though: when submitting a bug report please provide clear information about the circumstances and a simple example
which reproduces the problem.
The issue tracker is of course not empty now. We have many remaining “enhacement” issues which we’ll hopefully
can tackle in 2014 with your help.
For those who use older Python versions, please note that pytest is not automatically tested on python2.5 due to
virtualenv, setuptools and tox not supporting it anymore. Manual verification shows that it mostly works fine but it’s
not going to be part of the automated release process and thus likely to break in the future.
As usual, current docs are at
http://pytest.org
and you can upgrade from pypi via:

Particular thanks for helping with this release go to Anatoly Bubenkoff, Floris Bruynooghe, Marc Abramowitz, Ralph
Schmitt, Ronny Pfannschmidt, Donald Stufft, James Lan, Rob Dennis, Jason R. Coombs, Mathieu Agopian, Virgil
Dupras, Bruno Oliveira, Alex Gaynor and others.
12.11.1 2.5.0
• dropped python2.5 from automated release testing of pytest itself which means it’s probably going to break soon
(but still works with this release we believe).
• simplified and fixed implementation for calling finalizers when parametrized fixtures or function arguments are
involved. finalization is now performed lazily at setup time instead of in the “teardown phase”. While this
might sound odd at first, it helps to ensure that we are correctly handling setup/teardown even in complex code.
User-level code should not be affected unless it’s implementing the pytest_runtest_teardown hook and expecting
certain fixture instances are torn down within (very unlikely and would have been unreliable anyway).
• PR90: add –color=yes|no|auto option to force terminal coloring mode (“auto” is default). Thanks Marc
Abramowitz.
• fix issue319 - correctly show unicode in assertion errors. Many thanks to Floris Bruynooghe for the complete
PR. Also means we depend on py>=1.4.19 now.
• fix issue396 - correctly sort and finalize class-scoped parametrized tests independently from number of methods
on the class.
• refix issue323 in a better way – parametrization should now never cause Runtime Recursion errors because
the underlying algorithm for re-ordering tests per-scope/per-fixture is not recursive anymore (it was tail-call
recursive before which could lead to problems for more than >966 non-function scoped parameters).
• fix issue290 - there is preliminary support now for parametrizing with repeated same values (sometimes useful
to to test if calling a second time works as with the first time).
• close issue240 - document precisely how pytest module importing works, discuss the two common test directory
layouts, and how it interacts with PEP420-namespace packages.
• fix issue246 fix finalizer order to be LIFO on independent fixtures depending on a parametrized higher-than-
function scoped fixture. (was quite some effort so please bear with the complexity of this sentence :) Thanks
Ralph Schmitt for the precise failure example.
• fix issue244 by implementing special index for parameters to only use indices for paramentrized test ids
• fix issue287 by running all finalizers but saving the exception from the first failing finalizer and re-raising it
so teardown will still have failed. We reraise the first failing exception because it might be the cause for other
finalizers to fail.
• fix ordering when mock.patch or other standard decorator-wrappings are used with test methods. This fixues
issue346 and should help with random “xdist” collection failures. Thanks to Ronny Pfannschmidt and Donald
Stufft for helping to isolate it.
• fix issue357 - special case “-k” expressions to allow for filtering with simple strings that are not valid python
expressions. Examples: “-k 1.3” matches all tests parametrized with 1.3. “-k None” filters all tests that have
“None” in their name and conversely “-k ‘not None”’. Previously these examples would raise syntax errors.
• fix issue384 by removing the trial support code since the unittest compat enhancements allow trial to handle it
on its own
• don’t hide an ImportError when importing a plugin produces one. fixes issue375.
12.11. pytest-2.5.0: now down to ZERO reported bugs! 157

• fix issue275 - allow usefixtures and autouse fixtures for running doctest text files.
• fix issue380 by making –resultlog only rely on longrepr instead of the “reprcrash” attribute which only exists
sometimes.
• address issue122: allow @pytest.fixture(params=iterator) by exploding into a list early on.
• fix pexpect-3.0 compatibility for pytest’s own tests. (fixes issue386)
• allow nested parametrize-value markers, thanks James Lan for the PR.
• fix unicode handling with new monkeypatch.setattr(import_path, value) API. Thanks Rob Dennis. Fixes is-
sue371.
• fix unicode handling with junitxml, fixes issue368.
• In assertion rewriting mode on Python 2, fix the detection of coding cookies. See issue #330.
• make “–runxfail” turn imperative pytest.xfail calls into no ops (it already did neutralize pytest.mark.xfail mark-
ers)
• refine pytest / pkg_resources interactions: The AssertionRewritingHook PEP302 compliant loader now registers
itself with setuptools/pkg_resources properly so that the pkg_resources.resource_stream method works properly.
Fixes issue366. Thanks for the investigations and full PR to Jason R. Coombs.
• pytestconfig fixture is now session-scoped as it is the same object during the whole test run. Fixes issue370.
• avoid one surprising case of marker malfunction/confusion:
@pytest.mark.some(lambda arg: ...)
would not work correctly because pytest assumes @pytest.mark.some gets a function to be decorated already.
We now at least detect if this arg is an lambda and thus the example will work. Thanks Alex Gaynor for bringing
it up.
• xfail a test on pypy that checks wrong encoding/ascii (pypy does not error out). fixes issue385.
• internally make varnames() deal with classes’s __init__, although it’s not needed by pytest itself atm. Also fix
caching. Fixes issue376.
• fix issue221 - handle importing of namespace-package with no __init__.py properly.
• refactor internal FixtureRequest handling to avoid monkeypatching. One of the positive user-facing effects is
that the “request” object can now be used in closures.
• fixed version comparison in pytest.importskip(modname, minverstring)
• fix issue377 by clarifying in the nose-compat docs that pytest does not duplicate the unittest-API into the “plain”
namespace.
• fix verbose reporting for @mock’d test functions
12.12 pytest-2.4.2: colorama on windows, plugin/tmpdir fixes
pytest-2.4.2 is another bug-fixing release:

• on Windows require colorama and a newer py lib so that py.io.TerminalWriter() now uses colorama instead of
its own ctypes hacks. (fixes issue365) thanks Paul Moore for bringing it up.
• fix “-k” matching of tests where “repr” and “attr” and other names would cause wrong matches because of an
internal implementation quirk (don’t ask) which is now properly implemented. fixes issue345.

• avoid tmpdir fixture to create too long filenames especially when parametrization is used (issue354)
• fix pytest-pep8 and pytest-flakes / pytest interactions (collection names in mark plugin was assuming an item
always has a function which is not true for those plugins etc.) Thanks Andi Zeidler.
• introduce node.get_marker/node.add_marker API for plugins like pytest-pep8 and pytest-flakes to avoid the
messy details of the node.keywords pseudo-dicts. Adapted docs.
• remove attempt to “dup” stdout at startup as it’s icky. the normal capturing should catch enough possibilities of
tests messing up standard FDs.
• add pluginmanager.do_configure(config) as a link to config.do_configure() for plugin-compatibility
as usual, docs at http://pytest.org and upgrades via:
12.13 pytest-2.4.1: fixing three regressions compared to 2.3.5
pytest-2.4.1 is a quick follow up release to fix three regressions compared to 2.3.5 before they hit more people:
• When using parser.addoption() unicode arguments to the “type” keyword should also be converted to the re-
spective types. thanks Floris Bruynooghe, @dnozay. (fixes issue360 and issue362)
• fix dotted filename completion when using argcomplete thanks Anthon van der Neuth. (fixes issue361)
• fix regression when a 1-tuple (“arg”,) is used for specifying parametrization (the values of the parametrization
were passed nested in a tuple). Thanks Donald Stufft.
• also merge doc typo fixes, thanks Andy Dirnberger
as usual, docs at http://pytest.org and upgrades via:
12.14 pytest-2.4.0: new fixture features/hooks and bug fixes
The just released pytest-2.4.0 brings many improvements and numerous bug fixes while remaining plugin- and test-
suite compatible apart from a few supposedly very minor incompatibilities. See below for a full list of details. A few
feature highlights:
• new yield-style fixtures pytest.yield_fixture, allowing to use existing with-style context managers in fixture
functions.
• improved pdb support: import pdb ; pdb.set_trace() now works without requiring prior dis-
abling of stdout/stderr capturing. Also the --pdb options works now on collection and inter-
nal errors and we introduced a new experimental hook for IDEs/plugins to intercept debugging:
pytest_exception_interact(node, call, report).
• shorter monkeypatch variant to allow specifying an import path as a target, for example:
monkeypatch.setattr("requests.get", myfunc)
• better unittest/nose compatibility: all teardown methods are now only called if the corresponding setup method
succeeded.
12.13. pytest-2.4.1: fixing three regressions compared to 2.3.5 159

• integrate tab-completion on command line options if you have argcomplete configured.

• allow boolean expression directly with skipif/xfail if a “reason” is also specified.
• a new hook pytest_load_initial_conftests allows plugins like pytest-django to influence the envi-
ronment before conftest files import django.
• reporting: color the last line red or green depending if failures/errors occurred or everything passed.
The documentation has been updated to accomodate the changes, see http://pytest.org
To install or upgrade pytest:
Many thanks to all who helped, including Floris Bruynooghe, Brianna Laugher, Andreas Pelme, Anthon van
der Neut, Anatoly Bubenkoff, Vladimir Keleshev, Mathieu Agopian, Ronny Pfannschmidt, Christian Theunert
and many others.
may passing tests be with you,
holger krekel
12.14.1 Changes between 2.3.5 and 2.4
known incompatibilities:
• if calling –genscript from python2.7 or above, you only get a standalone script which works on python2.7 or
above. Use Python2.6 to also get a python2.5 compatible version.
• all xunit-style teardown methods (nose-style, pytest-style, unittest-style) will not be called if the corresponding
setup method failed, see issue322 below.
• the pytest_plugin_unregister hook wasn’t ever properly called and there is no known implementation of the hook
- so it got removed.
• pytest.fixture-decorated functions cannot be generators (i.e. use yield) anymore. This change might be re-
versed in 2.4.1 if it causes unforeseen real-life issues. However, you can always write and return an inner
function/generator and change the fixture consumer to iterate over the returned generator. This change was done
in lieu of the new pytest.yield_fixture decorator, see below.
new features:
• experimentally introduce a new pytest.yield_fixture decorator which accepts exactly the same pa-
rameters as pytest.fixture but mandates a yield statement instead of a return statement from fixture
functions. This allows direct integration with “with-style” context managers in fixture functions and generally
avoids registering of finalization callbacks in favour of treating the “after-yield” as teardown code. Thanks
Andreas Pelme, Vladimir Keleshev, Floris Bruynooghe, Ronny Pfannschmidt and many others for discussions.
• allow boolean expression directly with skipif/xfail if a “reason” is also specified. Rework skipping documen-
tation to recommend “condition as booleans” because it prevents surprises when importing markers between
modules. Specifying conditions as strings will remain fully supported.
• reporting: color the last line red or green depending if failures/errors occurred or everything passed. thanks
Christian Theunert.
• make “import pdb ; pdb.set_trace()” work natively wrt capturing (no “-s” needed anymore), making
pytest.set_trace() a mere shortcut.

• fix issue181: –pdb now also works on collect errors (and on internal errors) . This was implemented by a slight
internal refactoring and the introduction of a new hook pytest_exception_interact hook (see next
item).
• fix issue341: introduce new experimental hook for IDEs/terminals to intercept debugging:
• new monkeypatch.setattr() variant to provide a shorter invocation for patching out classes/functions from mod-
ules:
monkeypatch.setattr(“requests.get”, myfunc)
will replace the “get” function of the “requests” module with myfunc.
• fix issue322: tearDownClass is not run if setUpClass failed. Thanks Mathieu Agopian for the initial fix. Also
make all of pytest/nose finalizer mimick the same generic behaviour: if a setupX exists and fails, don’t run
teardownX. This internally introduces a new method “node.addfinalizer()” helper which can only be called
during the setup phase of a node.
• simplify pytest.mark.parametrize() signature: allow to pass a CSV-separated string to specify argnames. For
example: pytest.mark.parametrize("input,expected", [(1,2), (2,3)]) works as well
as the previous: pytest.mark.parametrize(("input", "expected"), ...).
• add support for setUpModule/tearDownModule detection, thanks Brian Okken.
• integrate tab-completion on options through use of “argcomplete”. Thanks Anthon van der Neut for the PR.
• change option names to be hyphen-separated long options but keep the old spelling backward compatible. py.test
-h will only show the hyphenated version, for example “–collect-only” but “–collectonly” will remain valid as
well (for backward-compat reasons). Many thanks to Anthon van der Neut for the implementation and to Hynek
Schlawack for pushing us.
• fix issue 308 - allow to mark/xfail/skip individual parameter sets when parametrizing. Thanks Brianna Laugher.
• call new experimental pytest_load_initial_conftests hook to allow 3rd party plugins to do something before a
conftest is loaded.
Bug fixes:
• fix issue358 - capturing options are now parsed more properly by using a new parser.parse_known_args method.
• pytest now uses argparse instead of optparse (thanks Anthon) which means that “argparse” is added as a depen-
dency if installing into python2.6 environments or below.
• fix issue333: fix a case of bad unittest/pytest hook interaction.
• PR27: correctly handle nose.SkipTest during collection. Thanks Antonio Cuni, Ronny Pfannschmidt.
• fix issue355: junitxml puts name=”pytest” attribute to testsuite tag.
• fix issue336: autouse fixture in plugins should work again.
• fix issue279: improve object comparisons on assertion failure for standard datatypes and recognise collec-
tions.abc. Thanks to Brianna Laugher and Mathieu Agopian.
• fix issue317: assertion rewriter support for the is_package method
• fix issue335: document py.code.ExceptionInfo() object returned from pytest.raises(), thanks Mathieu Agopian.
• remove implicit distribute_setup support from setup.py.
• fix issue305: ignore any problems when writing pyc files.
• SO-17664702: call fixture finalizers even if the fixture function partially failed (finalizers would not always be
called before)
12.14. pytest-2.4.0: new fixture features/hooks and bug fixes 161

• fix issue320 - fix class scope for fixtures when mixed with module-level functions. Thanks Anatloy Bubenkoff.
• you can specify “-q” or “-qq” to get different levels of “quieter” reporting (thanks Katarzyna Jachim)
• fix issue300 - Fix order of conftest loading when starting py.test in a subdirectory.
• fix issue323 - sorting of many module-scoped arg parametrizations
• make sessionfinish hooks execute with the same cwd-context as at session start (helps fix plugin behaviour
which write output files with relative path such as pytest-cov)
• fix issue316 - properly reference collection hooks in docs
• fix issue 306 - cleanup of -k/-m options to only match markers/test names/keywords respectively. Thanks Wouter
van Ackooy.
• improved doctest counting for doctests in python modules – files without any doctest items will not show up
anymore and doctest examples are counted as separate test items. thanks Danilo Bellini.
• fix issue245 by depending on the released py-1.4.14 which fixes py.io.dupfile to work with files with no mode.
Thanks Jason R. Coombs.
• fix junitxml generation when test output contains control characters, addressing issue267, thanks Jaap
Broekhuizen
• fix issue338: honor –tb style for setup/teardown errors as well. Thanks Maho.
• fix issue307 - use yaml.safe_load in example, thanks Mark Eichin.
• better parametrize error messages, thanks Brianna Laugher
• pytest_terminal_summary(terminalreporter) hooks can now use ”.section(title)” and ”.line(msg)” methods to
print extra information at the end of a test run.
12.15 pytest-2.3.5: bug fixes and little improvements
pytest-2.3.5 is a maintenance release with many bug fixes and little improvements. See the changelog below for details.
No backward compatibility issues are foreseen and all plugins which worked with the prior version are expected to
work unmodified. Speaking of which, a few interesting new plugins saw the light last month:
• pytest-instafail: show failure information while tests are running
• pytest-qt: testing of GUI applications written with QT/Pyside
• pytest-xprocess: managing external processes across test runs
• pytest-random: randomize test ordering
And several others like pytest-django saw maintenance releases. For a more complete list, check out
https://pypi.python.org/pypi?%3Aaction=search&term=pytest&submit=search.
For general information see:
http://pytest.org/
pip install -U pytest # or easy_install -U pytest
Particular thanks to Floris, Ronny, Benjamin and the many bug reporters and fix providers.
may the fixtures be with you, holger krekel

12.15.1 Changes between 2.3.4 and 2.3.5
• never consider a fixture function for test function collection

• allow re-running of test items / helps to fix pytest-reruntests plugin and also help to keep less fixture/resource
references alive
• put captured stdout/stderr into junitxml output even for passing tests (thanks Adam Goucher)
• Issue 265 - integrate nose setup/teardown with setupstate so it doesnt try to teardown if it did not setup
• issue 271 - dont write junitxml on slave nodes
• Issue 274 - dont try to show full doctest example when doctest does not know the example location
• issue 280 - disable assertion rewriting on buggy CPython 2.6.0
• inject “getfixture()” helper to retrieve fixtures from doctests, thanks Andreas Zeidler
• issue 259 - when assertion rewriting, be consistent with the default source encoding of ASCII on Python 2
• issue 251 - report a skip instead of ignoring classes with init
• issue250 unicode/str mixes in parametrization names and values now works
• issue257, assertion-triggered compilation of source ending in a comment line doesn’t blow up in python2.5
(fixed through py>=1.4.13.dev6)
• fix –genscript option to generate standalone scripts that also work with python3.3 (importer ordering)
• issue171 - in assertion rewriting, show the repr of some global variables
• fix option help for “-k”
• move long description of distribution into README.rst
• improve docstring for metafunc.parametrize()
• fix bug where using capsys with pytest.set_trace() in a test function would break when looking at cap-
sys.readouterr()
• allow to specify prefixes starting with “_” when customizing python_functions test discovery. (thanks Graham
Horler)
• improve PYTEST_DEBUG tracing output by puting extra data on a new lines with additional indent
• ensure OutcomeExceptions like skip/fail have initialized exception attributes
• issue 260 - don’t use nose special setup on plain unittest cases
• fix issue134 - print the collect errors that prevent running specified test items
• fix issue266 - accept unicode in MarkEvaluator expressions
12.16 pytest-2.3.4: stabilization, more flexible selection via “-k expr”
pytest-2.3.4 is a small stabilization release of the py.test tool which offers uebersimple assertions, scalable fixture
mechanisms and deep customization for testing with Python. This release comes with the following fixes and features:
• make “-k” option accept an expressions the same as with “-m” so that one can write: -k “name1 or name2” etc.
This is a slight usage incompatibility if you used special syntax like “TestClass.test_method” which you now
need to write as -k “TestClass and test_method” to match a certain method in a certain test class.
• allow to dynamically define markers via item.keywords[...]=assignment integrating with “-m” option
12.16. pytest-2.3.4: stabilization, more flexible selection via “-k expr” 163
• yielded test functions will now have autouse-fixtures active but cannot accept fixtures as funcargs
- it’s anyway recommended to rather use the post-2.0 parametrize features instead of yield, see:
http://pytest.org/latest/example/parametrize.html
• fix autouse-issue where autouse-fixtures would not be discovered if defined in a a/conftest.py file and tests in
a/tests/test_some.py
• fix issue226 - LIFO ordering for fixture teardowns
• fix issue224 - invocations with >256 char arguments now work
• fix issue91 - add/discuss package/directory level setups in example
• fixes related to autouse discovery and calling
Thanks in particular to Thomas Waldmann for spotting and reporting issues.
See
http://pytest.org/
for general information. To install or upgrade pytest:
best, holger krekel
12.17 pytest-2.3.3: integration fixes, py24 suport, */** shown in

traceback
pytest-2.3.3 is a another stabilization release of the py.test tool which offers uebersimple assertions, scalable fixture
mechanisms and deep customization for testing with Python. Particularly, this release provides:
• integration fixes and improvements related to flask, numpy, nose, unittest, mock
• makes pytest work on py24 again (yes, people sometimes still need to use it)
• show *,** args in pytest tracebacks
Thanks to Manuel Jacob, Thomas Waldmann, Ronny Pfannschmidt, Pavel Repin and Andreas Taumoefolau for pro-
viding patches and all for the issues.
See
http://pytest.org/
best, holger krekel
• fix issue214 - parse modules that contain special objects like e. g. flask’s request object which blows up on
getattr access if no request is active. thanks Thomas Waldmann.
• fix issue213 - allow to parametrize with values like numpy arrays that do not support an __eq__ operator
• fix issue215 - split test_python.org into multiple files

• fix issue148 - @unittest.skip on classes is now recognized and avoids calling setUpClass/tearDownClass, thanks
Pavel Repin
• fix issue209 - reintroduce python2.4 support by depending on newer pylib which re-introduced statement-finding
for pre-AST interpreters
• nose support: only call setup if its a callable, thanks Andrew Taumoefolau
• fix issue219 - add py2.4-3.3 classifiers to TROVE list
• in tracebacks ,* arg values are now shown next to normal arguments (thanks Manuel Jacob)
• fix issue217 - support mock.patch with pytest’s fixtures - note that you need either mock-1.0.1 or the python3.3
builtin unittest.mock.
• fix issue127 - improve documentation for pytest_addoption() and add a config.getoption(name) helper
function for consistency.
12.18 pytest-2.3.2: some fixes and more traceback-printing speed
pytest-2.3.2 is a another stabilization release:

• issue 205: fixes a regression with conftest detection
• issue 208/29: fixes traceback-printing speed in some bad cases
• fix teardown-ordering for parametrized setups
• fix unittest and trial compat behaviour with respect to runTest() methods
• issue 206 and others: some improvements to packaging
• fix issue127 and others: improve some docs
See
http://pytest.org/
best, holger krekel
• fix issue208 and fix issue29 use new py version to avoid long pauses when printing tracebacks in long modules
• fix issue205 - conftests in subdirs customizing pytest_pycollect_makemodule and pytest_pycollect_makeitem
now work properly
• fix issue127 - better documentation for pytest_addoption and related objects.
• fix unittest behaviour: TestCase.runtest only called if there are test methods defined
• improve trial support: don’t collect its empty unittest.TestCase.runTest() method
• “python setup.py test” now works with pytest itself
• fix/improve internal/packaging related bits:
– exception message check of test_nose.py now passes on python33 as well
12.18. pytest-2.3.2: some fixes and more traceback-printing speed 165

– issue206 - fix test_assertrewrite.py to work when a global PYTHONDONTWRITEBYTECODE=1 is

present
– add tox.ini to pytest distribution so that ignore-dirs and others config bits are properly distributed for
maintainers who run pytest-own tests
12.19 pytest-2.3.1: fix regression with factory functions
pytest-2.3.1 is a quick follow-up release:

• fix issue202 - regression with fixture functions/funcarg factories: using “self” is now safe again and works as in
2.2.4. Thanks to Eduard Schettino for the quick bug report.
• disable pexpect pytest self tests on Freebsd - thanks Koob for the quick reporting
• fix/improve interactive docs with –markers
See
http://pytest.org/
best, holger krekel
• fix issue202 - fix regression: using “self” from fixture functions now works as expected (it’s the same “self”
instance that a test method which uses the fixture sees)
• skip pexpect using tests (test_pdb.py mostly) on freebsd* systems due to pexpect not supporting it properly
(hanging)
• link to web pages from –markers output which provides help for pytest.mark.* usage.
12.20 pytest-2.3: improved fixtures / better unittest integration
pytest-2.3 comes with many major improvements for fixture/funcarg management and parametrized testing in Python.
It is now easier, more efficient and more predicatable to re-run the same tests with different fixture instances. Also,
you can directly declare the caching “scope” of fixtures so that dependent tests throughout your whole test suite can
re-use database or other expensive fixture objects with ease. Lastly, it’s possible for fixture functions (formerly known
as funcarg factories) to use other fixtures, allowing for a completely modular and re-useable fixture design.
For detailed info and tutorial-style examples, see:
http://pytest.org/latest/fixture.html
Moreover, there is now support for using pytest fixtures/funcargs with unittest-style suites, see here for examples:
http://pytest.org/latest/unittest.html
Besides, more unittest-test suites are now expected to “simply work” with pytest.
All changes are backward compatible and you should be able to continue to run your test suites and 3rd party plugins
that worked with pytest-2.2.4.

If you are interested in the precise reasoning (including examples) of the pytest-2.3 fixture evolution, please consult
http://pytest.org/latest/funcarg_compare.html
For general info on installation and getting started:
http://pytest.org/latest/getting-started.html
Docs and PDF access as usual at:
http://pytest.org
and more details for those already in the knowing of pytest can be found in the CHANGELOG below.
Particular thanks for this release go to Floris Bruynooghe, Alex Okrushko Carl Meyer, Ronny Pfannschmidt, Benjamin
Peterson and Alex Gaynor for helping to get the new features right and well integrated. Ronny and Floris also helped
to fix a number of bugs and yet more people helped by providing bug reports.
• fix issue202 - better automatic names for parametrized test functions

• fix issue139 - introduce @pytest.fixture which allows direct scoping and parametrization of funcarg factories.
Introduce new @pytest.setup marker to allow the writing of setup functions which accept funcargs.
• fix issue198 - conftest fixtures were not found on windows32 in some circumstances with nested directory
structures due to path manipulation issues
• fix issue193 skip test functions with were parametrized with empty parameter sets
• fix python3.3 compat, mostly reporting bits that previously depended on dict ordering
• introduce re-ordering of tests by resource and parametrization setup which takes precedence to the usual file-
ordering
• fix issue185 monkeypatching time.time does not cause pytest to fail
• fix issue172 duplicate call of pytest.setup-decoratored setup_module functions
• fix junitxml=path construction so that if tests change the current working directory and the path is a relative path
it is constructed correctly from the original current working dir.
• fix “python setup.py test” example to cause a proper “errno” return
• fix issue165 - fix broken doc links and mention stackoverflow for FAQ
• catch unicode-issues when writing failure representations to terminal to prevent the whole session from crashing
• fix xfail/skip confusion: a skip-mark or an imperative pytest.skip will now take precedence
before xfail-markers because we can’t determine xfail/xpass status in case of a skip. see
also: http://stackoverflow.com/questions/11105828/in-py-test-when-i-explicitly-skip-a-test-that-is-marked-as-
xfail-how-can-i-get
• always report installed 3rd party plugins in the header of a test run
• fix issue160: a failing setup of an xfail-marked tests should be reported as xfail (not xpass)
• fix issue128: show captured output when capsys/capfd are used
• fix issue179: propperly show the dependency chain of factories
• pluginmanager.register(...) now raises ValueError if the plugin has been already registered or the name is taken
• fix issue159: improve http://pytest.org/latest/faq.html especially with respect to the “magic” history, also men-
tion pytest-django, trial and unittest integration.
12.20. pytest-2.3: improved fixtures / better unittest integration 167

• make request.keywords and node.keywords writable. All descendant collection nodes will see keyword values.
Keywords are dictionaries containing markers and other info.
• fix issue 178: xml binary escapes are now wrapped in py.xml.raw
• fix issue 176: correctly catch the builtin AssertionError even when we replaced AssertionError with a subclass
on the python level
• factory discovery no longer fails with magic global callables that provide no sane __code__ object (mock.call
for example)
• fix issue 182: testdir.inprocess_run now considers passed plugins
• fix issue 188: ensure sys.exc_info is clear on python2 before calling into a test
• fix issue 191: add unittest TestCase runTest method support
• fix issue 156: monkeypatch correctly handles class level descriptors
• reporting refinements:
– pytest_report_header now receives a “startdir” so that you can use startdir.bestrelpath(yourpath) to show
nice relative path
– allow plugins to implement both pytest_report_header and pytest_sessionstart (sessionstart is invoked
first).
– don’t show deselected reason line if there is none
– py.test -vv will show all of assert comparisations instead of truncating
12.21 pytest-2.2.4: bug fixes, better junitxml/unittest/python3 compat
pytest-2.2.4 is a minor backward-compatible release of the versatile py.test testing tool. It contains bug fixes and a few
refinements to junitxml reporting, better unittest- and python3 compatibility.
For general information see here:
http://pytest.org/
Special thanks for helping on this release to Ronny Pfannschmidt and Benjamin Peterson and the contributors of issues.
best, holger krekel
• fix error message for rewritten assertions involving the % operator

• fix issue 126: correctly match all invalid xml characters for junitxml binary escape
• fix issue with unittest: now @unittest.expectedFailure markers should be processed correctly (you can also use
@pytest.mark markers)
• document integration with the extended distribute/setuptools test commands
• fix issue 140: propperly get the real functions of bound classmethods for setup/teardown_class
• fix issue #141: switch from the deceased paste.pocoo.org to bpaste.net

• fix issue #143: call unconfigure/sessionfinish always when configure/sessionstart where called
• fix issue #144: better mangle test ids to junitxml classnames
• upgrade distribute_setup.py to 0.6.27
12.22 pytest-2.2.2: bug fixes
pytest-2.2.2 (updated to 2.2.3 to fix packaging issues) is a minor backward-compatible release of the versatile py.test
testing tool. It contains bug fixes and a few refinements particularly to reporting with “–collectonly”, see below for
betails.
http://pytest.org/
Special thanks for helping on this release to Ronny Pfannschmidt and Ralf Schmitt and the contributors of issues.
best, holger krekel
• fix issue101: wrong args to unittest.TestCase test function now produce better output
• fix issue102: report more useful errors and hints for when a test directory was renamed and some
pyc/__pycache__ remain
• fix issue106: allow parametrize to be applied multiple times e.g. from module, class and at function level.
• fix issue107: actually perform session scope finalization
• don’t check in parametrize if indirect parameters are funcarg names
• add chdir method to monkeypatch funcarg
• fix crash resulting from calling monkeypatch undo a second time
• fix issue115: make –collectonly robust against early failure (missing files/directories)
• “-qq –collectonly” now shows only files and the number of tests in them
• “-q –collectonly” now shows test ids
• allow adding of attributes to test reports such that it also works with distributed testing (no upgrade of pytest-
xdist needed)
12.23 pytest-2.2.1: bug fixes, perfect teardowns
pytest-2.2.1 is a minor backward-compatible release of the the py.test testing tool. It contains bug fixes and little
improvements, including documentation fixes. If you are using the distributed testing pluginmake sure to upgrade it
to pytest-xdist-1.8.
http://pytest.org/
12.22. pytest-2.2.2: bug fixes 169


Special thanks for helping on this release to Ronny Pfannschmidt, Jurko Gospodnetic and Ralf Schmitt.
best, holger krekel
• fix issue99 (in pytest and py) internallerrors with resultlog now produce better output - fixed by normalizing
pytest_internalerror input arguments.
• fix issue97 / traceback issues (in pytest and py) improve traceback output in conjunction with jinja2 and cython
which hack tracebacks
• fix issue93 (in pytest and pytest-xdist) avoid “delayed teardowns”: the final test in a test node will now run
its teardown directly instead of waiting for the end of the session. Thanks Dave Hunt for the good reporting
and feedback. The pytest_runtest_protocol as well as the pytest_runtest_teardown hooks now have “nextitem”
available which will be None indicating the end of the test run.
• fix collection crash due to unknown-source collected items, thanks to Ralf Schmitt (fixed by depending on a
more recent pylib)
12.24 py.test 2.2.0: test marking++, parametrization++ and duration

profiling
pytest-2.2.0 is a test-suite compatible release of the popular py.test testing tool. Plugins might need upgrades. It comes
with these improvements:
• easier and more powerful parametrization of tests:
– new @pytest.mark.parametrize decorator to run tests with different arguments
– new metafunc.parametrize() API for parametrizing arguments independently
– see examples at http://pytest.org/latest/example/parametrize.html
– NOTE that parametrize() related APIs are still a bit experimental and might change in future releases.
• improved handling of test markers and refined marking mechanism:
– “-m markexpr” option for selecting tests according to their mark
– a new “markers” ini-variable for registering test markers for your project
– the new “–strict” bails out with an error if using unregistered markers.
– see examples at http://pytest.org/latest/example/markers.html
• duration profiling: new “–duration=N” option showing the N slowest test execution or setup/teardown calls.
This is most useful if you want to find out where your slowest test code is.
• also 2.2.0 performs more eager calling of teardown/finalizers functions resulting in better and more accurate
reporting when they fail
Besides there is the usual set of bug fixes along with a cleanup of pytest’s own test suite allowing it to run on a wider
range of environments.
For general information, see extensive docs with examples here:

http://pytest.org/
If you want to install or upgrade pytest you might just type:
Thanks to Ronny Pfannschmidt, David Burns, Jeff Donner, Daniel Nouri, Alfredo Deza and all who gave feedback or
sent bug reports.
best, holger krekel
12.24.1 notes on incompatibility
While test suites should work unchanged you might need to upgrade plugins:
• You need a new version of the pytest-xdist plugin (1.7) for distributing test runs.
• Other plugins might need an upgrade if they implement the pytest_runtest_logreport hook which
now is called unconditionally for the setup/teardown fixture phases of a test. You may choose to ignore
setup/teardown failures by inserting “if rep.when != ‘call’: return” or something similar. Note that most code
probably “just” works because the hook was already called for failing setup/teardown phases of a test so a plugin
should have been ready to grok such reports already.
• fix issue90: introduce eager tearing down of test items so that teardown function are called earlier.
• add an all-powerful metafunc.parametrize function which allows to parametrize test function arguments in mul-
tiple steps and therefore from independent plugins and places.
• add a @pytest.mark.parametrize helper which allows to easily call a test function with different argument values.
• Add examples to the “parametrize” example page, including a quick port of Test scenarios and the new
parametrize function and decorator.
• introduce registration for “pytest.mark.*” helpers via ini-files or through plugin hooks. Also introduce a “–strict”
option which will treat unregistered markers as errors allowing to avoid typos and maintain a well described set
of markers for your test suite. See examples at http://pytest.org/latest/mark.html and its links.
• issue50: introduce “-m marker” option to select tests based on markers (this is a stricter and more predictable
version of “-k” in that “-m” only matches complete markers and has more obvious rules for and/or semantics.
• new feature to help optimizing the speed of your tests: –durations=N option for displaying N slowest test calls
and setup/teardown methods.
• fix issue87: –pastebin now works with python3
• fix issue89: –pdb with unexpected exceptions in doctest work more sensibly
• fix and cleanup pytest’s own test suite to not leak FDs
• fix issue83: link to generated funcarg list
• fix issue74: pyarg module names are now checked against imp.find_module false positives
• fix compatibility with twisted/trial-11.1.0 use cases
12.24. py.test 2.2.0: test marking++, parametrization++ and duration profiling 171
12.25 py.test 2.1.3: just some more fixes
pytest-2.1.3 is a minor backward compatible maintenance release of the popular py.test testing tool. It is commonly
used for unit, functional- and integration testing. See extensive docs with examples here:
http://pytest.org/
The release contains another fix to the perfected assertions introduced with the 2.1 series as well as the new possibility
to customize reporting for assertion expressions on a per-directory level.
If you want to install or upgrade pytest, just type one of:
Thanks to the bug reporters and to Ronny Pfannschmidt, Benjamin Peterson and Floris Bruynooghe who implemented
the fixes.
best, holger krekel
• fix issue79: assertion rewriting failed on some comparisons in boolops,

• correctly handle zero length arguments (a la pytest ‘’)
• fix issue67 / junitxml now contains correct test durations
• fix issue75 / skipping test failure on jython
• fix issue77 / Allow assertrepr_compare hook to apply to a subset of tests
12.26 py.test 2.1.2: bug fixes and fixes for jython
pytest-2.1.2 is a minor backward compatible maintenance release of the popular py.test testing tool. pytest is commonly
used for unit, functional- and integration testing. See extensive docs with examples here:
http://pytest.org/
Most bug fixes address remaining issues with the perfected assertions introduced in the 2.1 series - many thanks to the
bug reporters and to Benjamin Peterson for helping to fix them. pytest should also work better with Jython-2.5.1 (and
Jython trunk).
best, holger krekel / http://merlinux.eu
• fix assertion rewriting on files with windows newlines on some Python versions
• refine test discovery by package/module name (–pyargs), thanks Florian Mayer
• fix issue69 / assertion rewriting fixed on some boolean operations

• fix issue68 / packages now work with assertion rewriting

• fix issue66: use different assertion rewriting caches when the -O option is passed
• don’t try assertion rewriting on Jython, use reinterp
12.27 py.test 2.1.1: assertion fixes and improved junitxml output
pytest-2.1.1 is a backward compatible maintenance release of the popular py.test testing tool. See extensive docs with
examples here:
http://pytest.org/
Most bug fixes address remaining issues with the perfected assertions introduced with 2.1.0 - many thanks to the bug
reporters and to Benjamin Peterson for helping to fix them. Also, junitxml output now produces system-out/err tags
which lead to better displays of tracebacks with Jenkins.
Also a quick note to package maintainers and others interested: there now is a “pytest” man page which can be
generated with “make man” in doc/.
• fix issue64 / pytest.set_trace now works within pytest_generate_tests hooks

• fix issue60 / fix error conditions involving the creation of __pycache__
• fix issue63 / assertion rewriting on inserts involving strings containing ‘%’
• fix assertion rewriting on calls with a ** arg
• don’t cache rewritten modules if bytecode generation is disabled
• fix assertion rewriting in read-only directories
• fix issue59: provide system-out/err tags for junitxml output
• fix issue61: assertion rewriting on boolean operations with 3 or more operands
• you can now build a man page with “cd doc ; make man”
12.28 py.test 2.1.0: perfected assertions and bug fixes
Welcome to the release of pytest-2.1, a mature testing tool for Python, supporting CPython 2.4-3.2, Jython and latest
PyPy interpreters. See the improved extensive docs (now also as PDF!) with tested examples here:
http://pytest.org/
The single biggest news about this release are perfected assertions courtesy of Benjamin Peterson. You can now
safely use assert statements in test modules without having to worry about side effects or python optimization
(“-OO”) options. This is achieved by rewriting assert statements in test modules upon import, using a PEP302 hook.
12.27. py.test 2.1.1: assertion fixes and improved junitxml output 173
See http://pytest.org/assert.html#advanced-assertion-introspection for detailed information. The work has been partly
sponsored by my company, merlinux GmbH.
For further details on bug fixes and smaller enhancements see below.
• fix issue53 call nosestyle setup functions with correct ordering

• fix issue58 and issue59: new assertion code fixes
• merge Benjamin’s assertionrewrite branch: now assertions for test modules on python 2.6 and above are done
by rewriting the AST and saving the pyc file before the test module is imported. see doc/assert.txt for more info.
• fix issue43: improve doctests with better traceback reporting on unexpected exceptions
• fix issue47: timing output in junitxml for test cases is now correct
• fix issue48: typo in MarkInfo repr leading to exception
• fix issue49: avoid confusing error when initialization partially fails
• fix issue44: env/username expansion for junitxml file path
• show releaselevel information in test runs for pypy
• reworked doc pages for better navigation and PDF generation
• report KeyboardInterrupt even if interrupted during session startup
• fix issue 35 - provide PDF doc version and download link from index page
12.29 py.test 2.0.3: bug fixes and speed ups
Welcome to pytest-2.0.3, a maintenance and bug fix release of pytest, a mature testing tool for Python, supporting
CPython 2.4-3.2, Jython and latest PyPy interpreters. See the extensive docs with tested examples here:
http://pytest.org/
There also is a bugfix release 1.6 of pytest-xdist, the plugin that enables seemless distributed and “looponfail” testing
for Python.
best, holger krekel

• fix issue38: nicer tracebacks on calls to hooks, particularly early configure/sessionstart ones
• fix missing skip reason/meta information in junitxml files, reported via http://lists.idyll.org/pipermail/testing-in-
python/2011-March/003928.html
• fix issue34: avoid collection failure with “test” prefixed classes deriving from object.
• don’t require zlib (and other libs) for genscript plugin without –genscript actually being used.
• speed up skips (by not doing a full traceback represenation internally)
• fix issue37: avoid invalid characters in junitxml’s output
12.30 py.test 2.0.2: bug fixes, improved xfail/skip expressions, speed

ups
CPython 2.4-3.2, Jython and latest PyPy interpreters. See the extensive docs with tested examples here:
http://pytest.org/
Many thanks to all issue reporters and people asking questions or complaining, particularly Jurko for his insistence,
Laura, Victor and Brianna for helping with improving and Ronny for his general advise.
best, holger krekel
• tackle issue32 - speed up test runs of very quick test functions by reducing the relative overhead
• fix issue30 - extended xfail/skipif handling and improved reporting. If you have a syntax error in your skip/xfail
expressions you now get nice error reports.
Also you can now access module globals from xfail/skipif expressions so that this for example works now:
import pytest
import mymodule
@pytest.mark.skipif("mymodule.__version__[0] == "1")
pass
This will not run the test function if the module’s version string does not start with a “1”. Note that specifying
a string instead of a boolean expressions allows py.test to report meaningful information when summarizing a
test run as to what conditions lead to skipping (or xfail-ing) tests.
• fix issue28 - setup_method and pytest_generate_tests work together The setup_method fixture method now gets
called also for test function invocations generated from the pytest_generate_tests hook.
• fix issue27 - collectonly and keyword-selection (-k) now work together Also, if you do “py.test –collectonly
-q” you now get a flat list of test ids that you can use to paste to the py.test commandline in order to execute a
particular test.
12.30. py.test 2.0.2: bug fixes, improved xfail/skip expressions, speed ups 175
• fix issue25 avoid reported problems with –pdb and python3.2/encodings output
• fix issue23 - tmpdir argument now works on Python3.2 and WindowsXP Starting with Python3.2 os.symlink
may be supported. By requiring a newer py lib version the py.path.local() implementation acknowledges this.
• fixed typos in the docs (thanks Victor Garcia, Brianna Laugher) and particular thanks to Laura Creighton who
also revieved parts of the documentation.
• fix slighly wrong output of verbose progress reporting for classes (thanks Amaury)
• more precise (avoiding of) deprecation warnings for node.Class|Function accesses
• avoid std unittest assertion helper code in tracebacks (thanks Ronny)
12.31 py.test 2.0.1: bug fixes
CPython 2.4-3.2, Jython and latest PyPy interpreters. See extensive docs with tested examples here:
http://pytest.org/
Many thanks to all issue reporters and people asking questions or complaining. Particular thanks to Floris Bruynooghe
and Ronny Pfannschmidt for their great coding contributions and many others for feedback and help.
best, holger krekel
• refine and unify initial capturing so that it works nicely even if the logging module is used on an early-loaded
conftest.py file or plugin.
• fix issue12 - show plugin versions with “–version” and “–traceconfig” and also document how to add extra
information to reporting test header
• fix issue17 (import-* reporting issue on python3) by requiring py>1.4.0 (1.4.1 is going to include it)
• fix issue10 (numpy arrays truth checking) by refining assertion interpretation in py lib
• fix issue15: make nose compatibility tests compatible with python3 (now that nose-1.0 supports python3)
• remove somewhat surprising “same-conftest” detection because it ignores conftest.py when they appear in sev-
eral subdirs.
• improve assertions (“not in”), thanks Floris Bruynooghe
• improve behaviour/warnings when running on top of “python -OO” (assertions and docstrings are turned off,
leading to potential false positives)
• introduce a pytest_cmdline_processargs(args) hook to allow dynamic computation of command line arguments.
This fixes a regression because py.test prior to 2.0 allowed to set command line options from conftest.py files
which so far pytest-2.0 only allowed from ini-files now.
• fix issue7: assert failures in doctest modules. unexpected failures in doctests will not generally show nicer, i.e.
within the doctest failing context.

• fix issue9: setup/teardown functions for an xfail-marked test will report as xfail if they fail but report as nor-
mally passing (not xpassing) if they succeed. This only is true for “direct” setup/teardown invocations because
teardown_class/ teardown_module cannot closely relate to a single test.
• fix issue14: no logging errors at process exit
• refinements to “collecting” output on non-ttys
• refine internal plugin registration and –traceconfig output
• introduce a mechanism to prevent/unregister plugins from the command line, see
http://pytest.org/latest/plugins.html#cmdunregister
• activate resultlog plugin by default
• fix regression wrt yielded tests which due to the collection-before-running semantics were not setup as with
pytest 1.3.4. Note, however, that the recommended and much cleaner way to do test parametrization remains
the “pytest_generate_tests” mechanism, see the docs.
12.32 py.test 2.0.0: asserts++, unittest++, reporting++, config++,

docs++
Welcome to pytest-2.0.0, a major new release of “py.test”, the rapid easy Python testing tool. There are many new
features and enhancements, see below for summary and detailed lists. A lot of long-deprecated code has been removed,
resulting in a much smaller and cleaner implementation. See the new docs with examples here:
http://pytest.org/2.0.0/index.html
A note on packaging: pytest used to part of the “py” distribution up until version py-1.3.4 but this has changed now:
pytest-2.0.0 only contains py.test related code and is expected to be backward-compatible to existing test code. If you
want to install pytest, just type one of:
Many thanks to all issue reporters and people asking questions or complaining. Particular thanks to Floris Bruynooghe
and Ronny Pfannschmidt for their great coding contributions and many others for feedback and help.
best, holger krekel
12.32.1 New Features
• new invocations through Python interpreter and from Python:

python -m pytest # on all pythons >= 2.5
or from a python program:

import pytest ; pytest.main(arglist, pluginlist)
see http://pytest.org/2.0.0/usage.html for details.

• new and better reporting information in assert expressions if comparing lists, sequences or strings.
see http://pytest.org/2.0.0/assert.html#newreport
• new configuration through ini-files (setup.cfg or tox.ini recognized), for example:
12.32. py.test 2.0.0: asserts++, unittest++, reporting++, config++, docs++ 177

[pytest]
norecursedirs = .hg data* # don't ever recurse in such dirs
addopts = -x --pyargs # add these command line options by default
see http://pytest.org/2.0.0/customize.html
• improved standard unittest support. In general py.test should now better be able to run custom unittest.TestCases
like twisted trial or Django based TestCases. Also you can now run the tests of an installed ‘unittest’ package
with py.test:
py.test --pyargs unittest
• new “-q” option which decreases verbosity and prints a more nose/unittest-style “dot” output.
• many many more detailed improvements details
12.32.2 Fixes
• fix issue126 - introduce py.test.set_trace() to trace execution via PDB during the running of tests even if capturing
is ongoing.
• fix issue124 - make reporting more resilient against tests opening files on filedescriptor 1 (stdout).
• fix issue109 - sibling conftest.py files will not be loaded. (and Directory collectors cannot be customized any-
more from a Directory’s conftest.py - this needs to happen at least one level up).
• fix issue88 (finding custom test nodes from command line arg)
• fix issue93 stdout/stderr is captured while importing conftest.py
• fix bug: unittest collected functions now also can have “pytestmark” applied at class/module level
12.32.3 Important Notes
• The usual way in pre-2.0 times to use py.test in python code was to import “py” and then e.g. use “py.test.raises”
for the helper. This remains valid and is not planned to be deprecated. However, in most examples and internal
code you’ll find “import pytest” and “pytest.raises” used as the recommended default way.
• pytest now first performs collection of the complete test suite before running any test. This changes for example
the semantics of when pytest_collectstart/pytest_collectreport are called. Some plugins may need upgrading.
• The pytest package consists of a 400 LOC core.py and about 20 builtin plugins, summing up to roughly 5000
LOCs, including docstrings. To be fair, it also uses generic code from the “pylib”, and the new “py” package to
help with filesystem and introspection/code manipulation.
12.32.4 (Incompatible) Removals
• py.test.config is now only available if you are in a test run.

• the following (mostly already deprecated) functionality was removed:
– removed support for Module/Class/... collection node definitions in conftest.py files. They will cause
nothing special.
– removed support for calling the pre-1.0 collection API of “run()” and “join”
– removed reading option values from conftest.py files or env variables. This can now be done much much
better and easier through the ini-file mechanism and the “addopts” entry in particular.

– removed the “disabled” attribute in test classes. Use the skipping and pytestmark mechanism to skip or
xfail a test class.
• py.test.collect.Directory does not exist anymore and it is not possible to provide an own “Directory” object. If
you have used this and don’t know what to do, get in contact. We’ll figure something out.
Note that pytest_collect_directory() is still called but any return value will be ignored. This allows to keep old
code working that performed for example “py.test.skip()” in collect() to prevent recursion into directory trees if
a certain dependency or command line option is missing.
see Changelog history for more detailed changes.
12.32. py.test 2.0.0: asserts++, unittest++, reporting++, config++, docs++ 179


CHAPTER
THIRTEEN
CHANGELOG HISTORY
13.1 2.7.1 (compared to 2.7.0)
• fix issue731: do not get confused by the braces which may be present and unbalanced in an object’s repr while
collapsing False explanations. Thanks Carl Meyer for the report and test case.
• fix issue553: properly handling inspect.getsourcelines failures in FixtureLookupError which would lead to to an
internal error, obfuscating the original problem. Thanks talljosh for initial diagnose/patch and Bruno Oliveira
for final patch.
• fix issue660: properly report scope-mismatch-access errors independently from ordering of fixture arguments.
Also avoid the pytest internal traceback which does not provide information to the user. Thanks Holger Krekel.
• streamlined and documented release process. Also all versions (in setup.py and documentation generation) are
now read from _pytest/__init__.py. Thanks Holger Krekel.
• fixed docs to remove the notion that yield-fixtures are experimental. They are here to stay :) Thanks Bruno
Oliveira.
• Support building wheels by using environment markers for the requirements. Thanks Ionel Maries Cristian.
• fixed regression to 2.6.4 which surfaced e.g. in lost stdout capture printing when tests raised SystemExit. Thanks
Holger Krekel.
• reintroduced _pytest fixture of the pytester plugin which is used at least by pytest-xdist.
13.2 2.7.0 (compared to 2.6.4)
• fix issue435: make reload() work when assert rewriting is active. Thanks Daniel Hahler.
• fix issue616: conftest.py files and their contained fixutres are now properly considered for visibility, indepen-
dently from the exact current working directory and test arguments that are used. Many thanks to Eric Siegerman
and his PR235 which contains systematic tests for conftest visibility and now passes. This change also intro-
duces the concept of a rootdir which is printed as a new pytest header and documented in the pytest customize
web page.
• change reporting of “diverted” tests, i.e. tests that are collected in one file but actually come from another (e.g.
when tests in a test class come from a base class in a different file). We now show the nodeid and indicate via a
postfix the other file.
• add ability to set command line options by environment variable PYTEST_ADDOPTS.
• added documentation on the new pytest-dev teams on bitbucket and github. See
https://pytest.org/latest/contributing.html . Thanks to Anatoly for pushing and initial work on this.
181
• fix issue650: new option --docttest-ignore-import-errors which will turn import errors in doctests
into skips. Thanks Charles Cloud for the complete PR.
• fix issue655: work around different ways that cause python2/3 to leak sys.exc_info into fixtures/tests causing
failures in 3rd party code
• fix issue615: assertion re-writing did not correctly escape % signs when formatting boolean operations, which
tripped over mixing booleans with modulo operators. Thanks to Tom Viner for the report, triaging and fix.
• implement issue351: add ability to specify parametrize ids as a callable to generate custom test ids. Thanks
Brianna Laugher for the idea and implementation.
• introduce and document new hookwrapper mechanism useful for plugins which want to wrap the execution
of certain hooks for their purposes. This supersedes the undocumented __multicall__ protocol which
pytest itself and some external plugins use. Note that pytest-2.8 is scheduled to drop supporting the old
__multicall__ and only support the hookwrapper protocol.
• majorly speed up invocation of plugin hooks
• use hookwrapper mechanism in builtin pytest plugins.
• add a doctest ini option for doctest flags, thanks Holger Peters.
• add note to docs that if you want to mark a parameter and the parameter is a callable, you also need to pass in a
reason to disambiguate it from the “decorator” case. Thanks Tom Viner.
• “python_classes” and “python_functions” options now support glob-patterns for test discovery, as discussed in
issue600. Thanks Ldiary Translations.
• allow to override parametrized fixtures with non-parametrized ones and vice versa (bubenkoff).
• fix issue463: raise specific error for ‘parameterize’ misspelling (pfctdayelise).
• On failure, the sys.last_value, sys.last_type and sys.last_traceback are set, so that a user
can inspect the error via postmortem debugging (almarklein).
13.3 2.6.4
• Improve assertion failure reporting on iterables, by using ndiff and pprint.

• removed outdated japanese docs from source tree.
• docs for “pytest_addhooks” hook. Thanks Bruno Oliveira.
• updated plugin index docs. Thanks Bruno Oliveira.
• fix issue557: with “-k” we only allow the old style “-” for negation at the beginning of strings and even that is
deprecated. Use “not” instead. This should allow to pick parametrized tests where “-” appeared in the parameter.
• fix issue604: Escape % character in the assertion message.
• fix issue620: add explanation in the –genscript target about what the binary blob means. Thanks Dinu Gherman.
• fix issue614: fixed pastebin support.
• fix issue620: add explanation in the –genscript target about what the binary blob means. Thanks Dinu Gherman.
• fix issue614: fixed pastebin support.
182 Chapter 13. Changelog history

13.4 2.6.3
• fix issue575: xunit-xml was reporting collection errors as failures instead of errors, thanks Oleg Sinyavskiy.
• fix issue582: fix setuptools example, thanks Laszlo Papp and Ronny Pfannschmidt.
• Fix infinite recursion bug when pickling capture.EncodedFile, thanks Uwe Schmitt.
• fix issue589: fix bad interaction with numpy and others when showing exceptions. Check for precise “maximum
recursion depth exceed” exception instead of presuming any RuntimeError is that one (implemented in py dep).
Thanks Charles Cloud for analysing the issue.
• fix conftest related fixture visibility issue: when running with a CWD outside a test package pytest would get
fixture discovery wrong. Thanks to Wolfgang Schnerring for figuring out a reproducable example.
• Introduce pytest_enter_pdb hook (needed e.g. by pytest_timeout to cancel the timeout when interactively enter-
ing pdb). Thanks Wolfgang Schnerring.
• check xfail/skip also with non-python function test items. Thanks Floris Bruynooghe.
13.5 2.6.2
• Added function pytest.freeze_includes(), which makes it easy to embed pytest into executables using tools like
cx_freeze. See docs for examples and rationale. Thanks Bruno Oliveira.
• Improve assertion rewriting cache invalidation precision.
• fixed issue561: adapt autouse fixture example for python3.
• fixed issue453: assertion rewriting issue with __repr__ containing “n{”, “n}” and “n~”.
• fix issue560: correctly display code if an “else:” or “finally:” is followed by statements on the same line.
• Fix example in monkeypatch documentation, thanks t-8ch.
• fix issue572: correct tmpdir doc example for python3.
• Do not mark as universal wheel because Python 2.6 is different from other builds due to the extra argparse
dependency. Fixes issue566. Thanks sontek.
• Implement issue549: user-provided assertion messages now no longer replace the py.test introspection message
but are shown in addition to them.
13.6 2.6.1
• No longer show line numbers in the –verbose output, the output is now purely the nodeid. The line number is
still shown in failure reports. Thanks Floris Bruynooghe.
• fix issue437 where assertion rewriting could cause pytest-xdist slaves to collect different tests. Thanks Bruno
Oliveira.
• fix issue555: add “errors” attribute to capture-streams to satisfy some distutils and possibly other code accessing
sys.stdout.errors.
• fix issue547 capsys/capfd also work when output capturing (“-s”) is disabled.
• address issue170: allow pytest.mark.xfail(...) to specify expected exceptions via an optional “raises=EXC”
argument where EXC can be a single exception or a tuple of exception classes. Thanks David Mohr for the
complete PR.
13.4. 2.6.3 183

• fix integration of pytest with unittest.mock.patch decorator when it uses the “new” argument. Thanks Nicolas
Delaby for test and PR.
• fix issue with detecting conftest files if the arguments contain ”::” node id specifications (copy pasted from “-v”
output)
• fix issue544 by only removing “@NUM” at the end of ”::” separated parts and if the part has an ”.py” extension
• don’t use py.std import helper, rather import things directly. Thanks Bruno Oliveira.
13.7 2.6
• Cache exceptions from fixtures according to their scope (issue 467).

• fix issue537: Avoid importing old assertion reinterpretation code by default.
• fix issue364: shorten and enhance tracebacks representation by default. The new “–tb=auto” option (default)
will only display long tracebacks for the first and last entry. You can get the old behaviour of printing all entries
as long entries with “–tb=long”. Also short entries by default are now printed very similarly to “–tb=native”
ones.
• fix issue514: teach assertion reinterpretation about private class attributes
• change -v output to include full node IDs of tests. Users can copy a node ID from a test run, including line
number, and use it as a positional argument in order to run only a single test.
• fix issue 475: fail early and comprehensible if calling pytest.raises with wrong exception type.
• fix issue516: tell in getting-started about current dependencies.
• cleanup setup.py a bit and specify supported versions. Thanks Jurko Gospodnetic for the PR.
• change XPASS colour to yellow rather then red when tests are run with -v.
• fix issue473: work around mock putting an unbound method into a class dict when double-patching.
• fix issue498: if a fixture finalizer fails, make sure that the fixture is still invalidated.
• fix issue453: the result of the pytest_assertrepr_compare hook now gets it’s newlines escaped so that for-
mat_exception does not blow up.
• internal new warning system: pytest will now produce warnings when it detects oddities in your test collection or
execution. Warnings are ultimately sent to a new pytest_logwarning hook which is currently only implemented
by the terminal plugin which displays warnings in the summary line and shows more details when -rw (report
on warnings) is specified.
• change skips into warnings for test classes with an __init__ and callables in test modules which look like a test
but are not functions.
• fix issue436: improved finding of initial conftest files from command line arguments by using the result of
parse_known_args rather than the previous flaky heuristics. Thanks Marc Abramowitz for tests and initial fixing
approaches in this area.
• fix issue #479: properly handle nose/unittest(2) SkipTest exceptions during collection/loading of test modules.
Thanks to Marc Schlaich for the complete PR.
• fix issue490: include pytest_load_initial_conftests in documentation and improve docstring.
• fix issue472: clarify that pytest.config.getvalue() cannot work if it’s triggered ahead of command
line parsing.
• merge PR123: improved integration with mock.patch decorator on tests.

• fix issue412: messing with stdout/stderr FD-level streams is now captured without crashes.
• fix issue483: trial/py33 works now properly. Thanks Daniel Grana for PR.
• improve example for pytest integration with “python setup.py test” which now has a generic “-a” or “–pytest-
args” option where you can pass additional options as a quoted string. Thanks Trevor Bekolay.
• simplified internal capturing mechanism and made it more robust against tests or setups changing FD1/FD2,
also better integrated now with pytest.pdb() in single tests.
• improvements to pytest’s own test-suite leakage detection, courtesy of PRs from Marc Abramowitz
• fix issue492: avoid leak in test_writeorg. Thanks Marc Abramowitz.
• fix issue493: don’t run tests in doc directory with python setup.py test (use tox -e doctesting for that)
• fix issue486: better reporting and handling of early conftest loading failures
• some cleanup and simplification of internal conftest handling.
• work a bit harder to break reference cycles when catching exceptions. Thanks Jurko Gospodnetic.
• fix issue443: fix skip examples to use proper comparison. Thanks Alex Groenholm.
• support nose-style __test__ attribute on modules, classes and functions, including unittest-style Classes. If
set to False, the test will not be collected.
• fix issue512: show “<notset>” for arguments which might not be set in monkeypatch plugin. Improves output
in documentation.
13.8 2.5.2
• fix issue409 – better interoperate with cx_freeze by not trying to import from collections.abc which causes
problems for py27/cx_freeze. Thanks Wolfgang L. for reporting and tracking it down.
• fixed docs and code to use “pytest” instead of “py.test” almost everywhere. Thanks Jurko Gospodnetic for the
complete PR.
• fix issue425: mention at end of “py.test -h” that –markers and –fixtures work according to specified test path (or
current dir)
• fix issue413: exceptions with unicode attributes are now printed correctly also on python2 and with pytest-xdist
runs. (the fix requires py-1.4.20)
• copy, cleanup and integrate py.io capture from pylib 1.4.20.dev2 (rev 13d9af95547e)
• address issue416: clarify docs as to conftest.py loading semantics
• fix issue429: comparing byte strings with non-ascii chars in assert expressions now work better. Thanks Floris
Bruynooghe.
• make capfd/capsys.capture private, its unused and shouldnt be exposed
13.9 2.5.1
• merge new documentation styling PR from Tobias Bieniek.

• fix issue403: allow parametrize of multiple same-name functions within a collection node. Thanks Andreas
Kloeckner and Alex Gaynor for reporting and analysis.
13.8. 2.5.2 185

• Allow parameterized fixtures to specify the ID of the parameters by adding an ids argument to pytest.fixture()
and pytest.yield_fixture(). Thanks Floris Bruynooghe.
• fix issue404 by always using the binary xml escape in the junitxml plugin. Thanks Ronny Pfannschmidt.
• fix issue407: fix addoption docstring to point to argparse instead of optparse. Thanks Daniel D. Wright.
13.10 2.5.0
• dropped python2.5 from automated release testing of pytest itself which means it’s probably going to break soon
(but still works with this release we believe).
• simplified and fixed implementation for calling finalizers when parametrized fixtures or function arguments are
involved. finalization is now performed lazily at setup time instead of in the “teardown phase”. While this
might sound odd at first, it helps to ensure that we are correctly handling setup/teardown even in complex code.
User-level code should not be affected unless it’s implementing the pytest_runtest_teardown hook and expecting
certain fixture instances are torn down within (very unlikely and would have been unreliable anyway).
• PR90: add –color=yes|no|auto option to force terminal coloring mode (“auto” is default). Thanks Marc
Abramowitz.
• fix issue319 - correctly show unicode in assertion errors. Many thanks to Floris Bruynooghe for the complete
PR. Also means we depend on py>=1.4.19 now.
• fix issue396 - correctly sort and finalize class-scoped parametrized tests independently from number of methods
on the class.
• refix issue323 in a better way – parametrization should now never cause Runtime Recursion errors because
the underlying algorithm for re-ordering tests per-scope/per-fixture is not recursive anymore (it was tail-call
recursive before which could lead to problems for more than >966 non-function scoped parameters).
• fix issue290 - there is preliminary support now for parametrizing with repeated same values (sometimes useful
to to test if calling a second time works as with the first time).
• close issue240 - document precisely how pytest module importing works, discuss the two common test directory
layouts, and how it interacts with PEP420-namespace packages.
• fix issue246 fix finalizer order to be LIFO on independent fixtures depending on a parametrized higher-than-
function scoped fixture. (was quite some effort so please bear with the complexity of this sentence :) Thanks
Ralph Schmitt for the precise failure example.
• fix issue244 by implementing special index for parameters to only use indices for paramentrized test ids
• fix issue287 by running all finalizers but saving the exception from the first failing finalizer and re-raising it
so teardown will still have failed. We reraise the first failing exception because it might be the cause for other
finalizers to fail.
• fix ordering when mock.patch or other standard decorator-wrappings are used with test methods. This fixues
issue346 and should help with random “xdist” collection failures. Thanks to Ronny Pfannschmidt and Donald
Stufft for helping to isolate it.
• fix issue357 - special case “-k” expressions to allow for filtering with simple strings that are not valid python
expressions. Examples: “-k 1.3” matches all tests parametrized with 1.3. “-k None” filters all tests that have
“None” in their name and conversely “-k ‘not None”’. Previously these examples would raise syntax errors.
• fix issue384 by removing the trial support code since the unittest compat enhancements allow trial to handle it
on its own
• don’t hide an ImportError when importing a plugin produces one. fixes issue375.
• fix issue275 - allow usefixtures and autouse fixtures for running doctest text files.

• fix issue380 by making –resultlog only rely on longrepr instead of the “reprcrash” attribute which only exists
sometimes.
• address issue122: allow @pytest.fixture(params=iterator) by exploding into a list early on.
• fix pexpect-3.0 compatibility for pytest’s own tests. (fixes issue386)
• allow nested parametrize-value markers, thanks James Lan for the PR.
• fix unicode handling with new monkeypatch.setattr(import_path, value) API. Thanks Rob Dennis. Fixes is-
sue371.
• fix unicode handling with junitxml, fixes issue368.
• In assertion rewriting mode on Python 2, fix the detection of coding cookies. See issue #330.
• make “–runxfail” turn imperative pytest.xfail calls into no ops (it already did neutralize pytest.mark.xfail mark-
ers)
• refine pytest / pkg_resources interactions: The AssertionRewritingHook PEP302 compliant loader now registers
itself with setuptools/pkg_resources properly so that the pkg_resources.resource_stream method works properly.
Fixes issue366. Thanks for the investigations and full PR to Jason R. Coombs.
• pytestconfig fixture is now session-scoped as it is the same object during the whole test run. Fixes issue370.
• avoid one surprising case of marker malfunction/confusion:
@pytest.mark.some(lambda arg: ...)
would not work correctly because pytest assumes @pytest.mark.some gets a function to be decorated already.
We now at least detect if this arg is an lambda and thus the example will work. Thanks Alex Gaynor for bringing
it up.
• xfail a test on pypy that checks wrong encoding/ascii (pypy does not error out). fixes issue385.
• internally make varnames() deal with classes’s __init__, although it’s not needed by pytest itself atm. Also fix
caching. Fixes issue376.
• fix issue221 - handle importing of namespace-package with no __init__.py properly.
• refactor internal FixtureRequest handling to avoid monkeypatching. One of the positive user-facing effects is
that the “request” object can now be used in closures.
• fixed version comparison in pytest.importskip(modname, minverstring)
• fix issue377 by clarifying in the nose-compat docs that pytest does not duplicate the unittest-API into the “plain”
namespace.
• fix verbose reporting for @mock’d test functions
13.11 v2.4.2
• on Windows require colorama and a newer py lib so that py.io.TerminalWriter() now uses colorama instead of
its own ctypes hacks. (fixes issue365) thanks Paul Moore for bringing it up.
• fix “-k” matching of tests where “repr” and “attr” and other names would cause wrong matches because of an
internal implementation quirk (don’t ask) which is now properly implemented. fixes issue345.
• avoid tmpdir fixture to create too long filenames especially when parametrization is used (issue354)
• fix pytest-pep8 and pytest-flakes / pytest interactions (collection names in mark plugin was assuming an item
always has a function which is not true for those plugins etc.) Thanks Andi Zeidler.
13.11. v2.4.2 187

• introduce node.get_marker/node.add_marker API for plugins like pytest-pep8 and pytest-flakes to avoid the
messy details of the node.keywords pseudo-dicts. Adapted docs.
• remove attempt to “dup” stdout at startup as it’s icky. the normal capturing should catch enough possibilities of
tests messing up standard FDs.
• add pluginmanager.do_configure(config) as a link to config.do_configure() for plugin-compatibility
13.12 v2.4.1
• When using parser.addoption() unicode arguments to the “type” keyword should also be converted to the re-
spective types. thanks Floris Bruynooghe, @dnozay. (fixes issue360 and issue362)
• fix dotted filename completion when using argcomplete thanks Anthon van der Neuth. (fixes issue361)
• fix regression when a 1-tuple (“arg”,) is used for specifying parametrization (the values of the parametrization
were passed nested in a tuple). Thanks Donald Stufft.
• merge doc typo fixes, thanks Andy Dirnberger
13.13 v2.4
known incompatibilities:
• if calling –genscript from python2.7 or above, you only get a standalone script which works on python2.7 or
above. Use Python2.6 to also get a python2.5 compatible version.
• all xunit-style teardown methods (nose-style, pytest-style, unittest-style) will not be called if the corresponding
setup method failed, see issue322 below.
• the pytest_plugin_unregister hook wasn’t ever properly called and there is no known implementation of the hook
- so it got removed.
• pytest.fixture-decorated functions cannot be generators (i.e. use yield) anymore. This change might be re-
versed in 2.4.1 if it causes unforeseen real-life issues. However, you can always write and return an inner
function/generator and change the fixture consumer to iterate over the returned generator. This change was done
in lieu of the new pytest.yield_fixture decorator, see below.
new features:
• experimentally introduce a new pytest.yield_fixture decorator which accepts exactly the same pa-
rameters as pytest.fixture but mandates a yield statement instead of a return statement from fixture
functions. This allows direct integration with “with-style” context managers in fixture functions and generally
avoids registering of finalization callbacks in favour of treating the “after-yield” as teardown code. Thanks
Andreas Pelme, Vladimir Keleshev, Floris Bruynooghe, Ronny Pfannschmidt and many others for discussions.
• allow boolean expression directly with skipif/xfail if a “reason” is also specified. Rework skipping documen-
tation to recommend “condition as booleans” because it prevents surprises when importing markers between
modules. Specifying conditions as strings will remain fully supported.
• reporting: color the last line red or green depending if failures/errors occurred or everything passed. thanks
Christian Theunert.
• make “import pdb ; pdb.set_trace()” work natively wrt capturing (no “-s” needed anymore), making
pytest.set_trace() a mere shortcut.

• fix issue181: –pdb now also works on collect errors (and on internal errors) . This was implemented by a slight
internal refactoring and the introduction of a new hook pytest_exception_interact hook (see next
item).
• fix issue341: introduce new experimental hook for IDEs/terminals to intercept debugging:
• new monkeypatch.setattr() variant to provide a shorter invocation for patching out classes/functions from mod-
ules:
monkeypatch.setattr(“requests.get”, myfunc)
will replace the “get” function of the “requests” module with myfunc.
• fix issue322: tearDownClass is not run if setUpClass failed. Thanks Mathieu Agopian for the initial fix. Also
make all of pytest/nose finalizer mimick the same generic behaviour: if a setupX exists and fails, don’t run
teardownX. This internally introduces a new method “node.addfinalizer()” helper which can only be called
during the setup phase of a node.
• simplify pytest.mark.parametrize() signature: allow to pass a CSV-separated string to specify argnames. For
example: pytest.mark.parametrize("input,expected", [(1,2), (2,3)]) works as well
as the previous: pytest.mark.parametrize(("input", "expected"), ...).
• add support for setUpModule/tearDownModule detection, thanks Brian Okken.
• integrate tab-completion on options through use of “argcomplete”. Thanks Anthon van der Neut for the PR.
• change option names to be hyphen-separated long options but keep the old spelling backward compatible. py.test
-h will only show the hyphenated version, for example “–collect-only” but “–collectonly” will remain valid as
well (for backward-compat reasons). Many thanks to Anthon van der Neut for the implementation and to Hynek
Schlawack for pushing us.
• fix issue 308 - allow to mark/xfail/skip individual parameter sets when parametrizing. Thanks Brianna Laugher.
• call new experimental pytest_load_initial_conftests hook to allow 3rd party plugins to do something before a
conftest is loaded.
Bug fixes:
• fix issue358 - capturing options are now parsed more properly by using a new parser.parse_known_args method.
• pytest now uses argparse instead of optparse (thanks Anthon) which means that “argparse” is added as a depen-
dency if installing into python2.6 environments or below.
• fix issue333: fix a case of bad unittest/pytest hook interaction.
• PR27: correctly handle nose.SkipTest during collection. Thanks Antonio Cuni, Ronny Pfannschmidt.
• fix issue355: junitxml puts name=”pytest” attribute to testsuite tag.
• fix issue336: autouse fixture in plugins should work again.
• fix issue279: improve object comparisons on assertion failure for standard datatypes and recognise collec-
tions.abc. Thanks to Brianna Laugher and Mathieu Agopian.
• fix issue317: assertion rewriter support for the is_package method
• fix issue335: document py.code.ExceptionInfo() object returned from pytest.raises(), thanks Mathieu Agopian.
• remove implicit distribute_setup support from setup.py.
• fix issue305: ignore any problems when writing pyc files.
• SO-17664702: call fixture finalizers even if the fixture function partially failed (finalizers would not always be
called before)
13.13. v2.4 189

• fix issue320 - fix class scope for fixtures when mixed with module-level functions. Thanks Anatloy Bubenkoff.
• you can specify “-q” or “-qq” to get different levels of “quieter” reporting (thanks Katarzyna Jachim)
• fix issue300 - Fix order of conftest loading when starting py.test in a subdirectory.
• fix issue323 - sorting of many module-scoped arg parametrizations
• make sessionfinish hooks execute with the same cwd-context as at session start (helps fix plugin behaviour
which write output files with relative path such as pytest-cov)
• fix issue316 - properly reference collection hooks in docs
• fix issue 306 - cleanup of -k/-m options to only match markers/test names/keywords respectively. Thanks Wouter
van Ackooy.
• improved doctest counting for doctests in python modules – files without any doctest items will not show up
anymore and doctest examples are counted as separate test items. thanks Danilo Bellini.
• fix issue245 by depending on the released py-1.4.14 which fixes py.io.dupfile to work with files with no mode.
Thanks Jason R. Coombs.
• fix junitxml generation when test output contains control characters, addressing issue267, thanks Jaap
Broekhuizen
• fix issue338: honor –tb style for setup/teardown errors as well. Thanks Maho.
• fix issue307 - use yaml.safe_load in example, thanks Mark Eichin.
• better parametrize error messages, thanks Brianna Laugher
• pytest_terminal_summary(terminalreporter) hooks can now use ”.section(title)” and ”.line(msg)” methods to
print extra information at the end of a test run.
13.14 v2.3.5
• fix issue169: respect –tb=style with setup/teardown errors as well.

• never consider a fixture function for test function collection
• allow re-running of test items / helps to fix pytest-reruntests plugin and also help to keep less fixture/resource
references alive
• put captured stdout/stderr into junitxml output even for passing tests (thanks Adam Goucher)
• Issue 265 - integrate nose setup/teardown with setupstate so it doesnt try to teardown if it did not setup
• issue 271 - dont write junitxml on slave nodes
• Issue 274 - dont try to show full doctest example when doctest does not know the example location
• issue 280 - disable assertion rewriting on buggy CPython 2.6.0
• inject “getfixture()” helper to retrieve fixtures from doctests, thanks Andreas Zeidler
• issue 259 - when assertion rewriting, be consistent with the default source encoding of ASCII on Python 2
• issue 251 - report a skip instead of ignoring classes with init
• issue250 unicode/str mixes in parametrization names and values now works
• issue257, assertion-triggered compilation of source ending in a comment line doesn’t blow up in python2.5
(fixed through py>=1.4.13.dev6)
• fix –genscript option to generate standalone scripts that also work with python3.3 (importer ordering)

• issue171 - in assertion rewriting, show the repr of some global variables

• fix option help for “-k”
• move long description of distribution into README.rst
• improve docstring for metafunc.parametrize()
• fix bug where using capsys with pytest.set_trace() in a test function would break when looking at cap-
sys.readouterr()
• allow to specify prefixes starting with “_” when customizing python_functions test discovery. (thanks Graham
Horler)
• improve PYTEST_DEBUG tracing output by puting extra data on a new lines with additional indent
• ensure OutcomeExceptions like skip/fail have initialized exception attributes
• issue 260 - don’t use nose special setup on plain unittest cases
• fix issue134 - print the collect errors that prevent running specified test items
• fix issue266 - accept unicode in MarkEvaluator expressions
13.15 v2.3.4
• yielded test functions will now have autouse-fixtures active but cannot accept fixtures as funcargs
- it’s anyway recommended to rather use the post-2.0 parametrize features instead of yield, see:
http://pytest.org/latest/example/parametrize.html
• fix autouse-issue where autouse-fixtures would not be discovered if defined in a a/conftest.py file and tests in
a/tests/test_some.py
• fix issue226 - LIFO ordering for fixture teardowns
• fix issue224 - invocations with >256 char arguments now work
• fix issue91 - add/discuss package/directory level setups in example
• allow to dynamically define markers via item.keywords[...]=assignment integrating with “-m” option
• make “-k” accept an expressions the same as with “-m” so that one can write: -k “name1 or name2” etc. This is
a slight incompatibility if you used special syntax like “TestClass.test_method” which you now need to write as
-k “TestClass and test_method” to match a certain method in a certain test class.
13.16 v2.3.3
• fix issue214 - parse modules that contain special objects like e. g. flask’s request object which blows up on
getattr access if no request is active. thanks Thomas Waldmann.
• fix issue213 - allow to parametrize with values like numpy arrays that do not support an __eq__ operator
• fix issue215 - split test_python.org into multiple files
• fix issue148 - @unittest.skip on classes is now recognized and avoids calling setUpClass/tearDownClass, thanks
Pavel Repin
• fix issue209 - reintroduce python2.4 support by depending on newer pylib which re-introduced statement-finding
for pre-AST interpreters
• nose support: only call setup if its a callable, thanks Andrew Taumoefolau
13.15. v2.3.4 191

• fix issue219 - add py2.4-3.3 classifiers to TROVE list

• in tracebacks ,* arg values are now shown next to normal arguments (thanks Manuel Jacob)
• fix issue217 - support mock.patch with pytest’s fixtures - note that you need either mock-1.0.1 or the python3.3
builtin unittest.mock.
• fix issue127 - improve documentation for pytest_addoption() and add a config.getoption(name) helper
function for consistency.
13.17 v2.3.2
• fix issue208 and fix issue29 use new py version to avoid long pauses when printing tracebacks in long modules
• fix issue205 - conftests in subdirs customizing pytest_pycollect_makemodule and pytest_pycollect_makeitem
now work properly
• fix issue127 - better documentation for pytest_addoption and related objects.
• fix unittest behaviour: TestCase.runtest only called if there are test methods defined
• improve trial support: don’t collect its empty unittest.TestCase.runTest() method
• “python setup.py test” now works with pytest itself
• fix/improve internal/packaging related bits:
– exception message check of test_nose.py now passes on python33 as well
– issue206 - fix test_assertrewrite.py to work when a global PYTHONDONTWRITEBYTECODE=1 is
present
– add tox.ini to pytest distribution so that ignore-dirs and others config bits are properly distributed for
maintainers who run pytest-own tests
13.18 v2.3.1
• fix issue202 - fix regression: using “self” from fixture functions now works as expected (it’s the same “self”
instance that a test method which uses the fixture sees)
• skip pexpect using tests (test_pdb.py mostly) on freebsd* systems due to pexpect not supporting it properly
(hanging)
• link to web pages from –markers output which provides help for pytest.mark.* usage.
13.19 v2.3.0
• fix issue202 - better automatic names for parametrized test functions

• fix issue139 - introduce @pytest.fixture which allows direct scoping and parametrization of funcarg factories.
• fix issue198 - conftest fixtures were not found on windows32 in some circumstances with nested directory
structures due to path manipulation issues
• fix issue193 skip test functions with were parametrized with empty parameter sets

• fix python3.3 compat, mostly reporting bits that previously depended on dict ordering
• introduce re-ordering of tests by resource and parametrization setup which takes precedence to the usual file-
ordering
• fix issue185 monkeypatching time.time does not cause pytest to fail
• fix issue172 duplicate call of pytest.fixture decoratored setup_module functions
• fix junitxml=path construction so that if tests change the current working directory and the path is a relative path
it is constructed correctly from the original current working dir.
• fix “python setup.py test” example to cause a proper “errno” return
• fix issue165 - fix broken doc links and mention stackoverflow for FAQ
• catch unicode-issues when writing failure representations to terminal to prevent the whole session from crashing
• fix xfail/skip confusion: a skip-mark or an imperative pytest.skip will now take precedence
before xfail-markers because we can’t determine xfail/xpass status in case of a skip. see
also: http://stackoverflow.com/questions/11105828/in-py-test-when-i-explicitly-skip-a-test-that-is-marked-as-
xfail-how-can-i-get
• always report installed 3rd party plugins in the header of a test run
• fix issue160: a failing setup of an xfail-marked tests should be reported as xfail (not xpass)
• fix issue128: show captured output when capsys/capfd are used
• fix issue179: propperly show the dependency chain of factories
• pluginmanager.register(...) now raises ValueError if the plugin has been already registered or the name is taken
• fix issue159: improve http://pytest.org/latest/faq.html especially with respect to the “magic” history, also men-
tion pytest-django, trial and unittest integration.
• make request.keywords and node.keywords writable. All descendant collection nodes will see keyword values.
Keywords are dictionaries containing markers and other info.
• fix issue 178: xml binary escapes are now wrapped in py.xml.raw
• fix issue 176: correctly catch the builtin AssertionError even when we replaced AssertionError with a subclass
on the python level
• factory discovery no longer fails with magic global callables that provide no sane __code__ object (mock.call
for example)
• fix issue 182: testdir.inprocess_run now considers passed plugins
• fix issue 188: ensure sys.exc_info is clear on python2 before calling into a test
• fix issue 191: add unittest TestCase runTest method support
• fix issue 156: monkeypatch correctly handles class level descriptors
• reporting refinements:
– pytest_report_header now receives a “startdir” so that you can use startdir.bestrelpath(yourpath) to show
nice relative path
– allow plugins to implement both pytest_report_header and pytest_sessionstart (sessionstart is invoked
first).
– don’t show deselected reason line if there is none
– py.test -vv will show all of assert comparisations instead of truncating
13.19. v2.3.0 193

13.20 v2.2.4
• fix error message for rewritten assertions involving the % operator

• fix issue 126: correctly match all invalid xml characters for junitxml binary escape
• fix issue with unittest: now @unittest.expectedFailure markers should be processed correctly (you can also use
@pytest.mark markers)
• document integration with the extended distribute/setuptools test commands
• fix issue 140: propperly get the real functions of bound classmethods for setup/teardown_class
• fix issue #141: switch from the deceased paste.pocoo.org to bpaste.net
• fix issue #143: call unconfigure/sessionfinish always when configure/sessionstart where called
• fix issue #144: better mangle test ids to junitxml classnames
• upgrade distribute_setup.py to 0.6.27
13.21 v2.2.3
• fix uploaded package to only include neccesary files
13.22 v2.2.2
• fix issue101: wrong args to unittest.TestCase test function now produce better output
• fix issue102: report more useful errors and hints for when a test directory was renamed and some
pyc/__pycache__ remain
• fix issue106: allow parametrize to be applied multiple times e.g. from module, class and at function level.
• fix issue107: actually perform session scope finalization
• don’t check in parametrize if indirect parameters are funcarg names
• add chdir method to monkeypatch funcarg
• fix crash resulting from calling monkeypatch undo a second time
• fix issue115: make –collectonly robust against early failure (missing files/directories)
• “-qq –collectonly” now shows only files and the number of tests in them
• “-q –collectonly” now shows test ids
• allow adding of attributes to test reports such that it also works with distributed testing (no upgrade of pytest-
xdist needed)
13.23 v2.2.1
• fix issue99 (in pytest and py) internallerrors with resultlog now produce better output - fixed by normalizing
pytest_internalerror input arguments.
• fix issue97 / traceback issues (in pytest and py) improve traceback output in conjunction with jinja2 and cython
which hack tracebacks

• fix issue93 (in pytest and pytest-xdist) avoid “delayed teardowns”: the final test in a test node will now run
its teardown directly instead of waiting for the end of the session. Thanks Dave Hunt for the good reporting
and feedback. The pytest_runtest_protocol as well as the pytest_runtest_teardown hooks now have “nextitem”
available which will be None indicating the end of the test run.
• fix collection crash due to unknown-source collected items, thanks to Ralf Schmitt (fixed by depending on a
more recent pylib)
13.24 v2.2.0
• fix issue90: introduce eager tearing down of test items so that teardown function are called earlier.
• add an all-powerful metafunc.parametrize function which allows to parametrize test function arguments in mul-
tiple steps and therefore from indepdenent plugins and palces.
• add a @pytest.mark.parametrize helper which allows to easily call a test function with different argument values
• Add examples to the “parametrize” example page, including a quick port of Test scenarios and the new
parametrize function and decorator.
• introduce registration for “pytest.mark.*” helpers via ini-files or through plugin hooks. Also introduce a “–strict”
option which will treat unregistered markers as errors allowing to avoid typos and maintain a well described set
of markers for your test suite. See exaples at http://pytest.org/latest/mark.html and its links.
• issue50: introduce “-m marker” option to select tests based on markers (this is a stricter and more predictable
version of ‘-k’ in that “-m” only matches complete markers and has more obvious rules for and/or semantics.
• new feature to help optimizing the speed of your tests: –durations=N option for displaying N slowest test calls
and setup/teardown methods.
• fix issue87: –pastebin now works with python3
• fix issue89: –pdb with unexpected exceptions in doctest work more sensibly
• fix and cleanup pytest’s own test suite to not leak FDs
• fix issue83: link to generated funcarg list
• fix issue74: pyarg module names are now checked against imp.find_module false positives
• fix compatibility with twisted/trial-11.1.0 use cases
• simplify Node.listchain
• simplify junitxml output code by relying on py.xml
• add support for skip properties on unittest classes and functions
13.25 v2.1.3
• fix issue79: assertion rewriting failed on some comparisons in boolops

• correctly handle zero length arguments (a la pytest ‘’)
• fix issue67 / junitxml now contains correct test durations, thanks ronny
• fix issue75 / skipping test failure on jython
• fix issue77 / Allow assertrepr_compare hook to apply to a subset of tests
13.24. v2.2.0 195

13.26 v2.1.2
• fix assertion rewriting on files with windows newlines on some Python versions
• refine test discovery by package/module name (–pyargs), thanks Florian Mayer
• fix issue69 / assertion rewriting fixed on some boolean operations
• fix issue68 / packages now work with assertion rewriting
• fix issue66: use different assertion rewriting caches when the -O option is passed
• don’t try assertion rewriting on Jython, use reinterp
13.27 v2.1.1
• fix issue64 / pytest.set_trace now works within pytest_generate_tests hooks

• fix issue60 / fix error conditions involving the creation of __pycache__
• fix issue63 / assertion rewriting on inserts involving strings containing ‘%’
• fix assertion rewriting on calls with a ** arg
• don’t cache rewritten modules if bytecode generation is disabled
• fix assertion rewriting in read-only directories
• fix issue59: provide system-out/err tags for junitxml output
• fix issue61: assertion rewriting on boolean operations with 3 or more operands
• you can now build a man page with “cd doc ; make man”
13.28 v2.1.0
• fix issue53 call nosestyle setup functions with correct ordering

• fix issue58 and issue59: new assertion code fixes
• merge Benjamin’s assertionrewrite branch: now assertions for test modules on python 2.6 and above are done
by rewriting the AST and saving the pyc file before the test module is imported. see doc/assert.txt for more info.
• fix issue43: improve doctests with better traceback reporting on unexpected exceptions
• fix issue47: timing output in junitxml for test cases is now correct
• fix issue48: typo in MarkInfo repr leading to exception
• fix issue49: avoid confusing error when initizaliation partially fails
• fix issue44: env/username expansion for junitxml file path
• show releaselevel information in test runs for pypy
• reworked doc pages for better navigation and PDF generation
• report KeyboardInterrupt even if interrupted during session startup
• fix issue 35 - provide PDF doc version and download link from index page

13.29 v2.0.3
• fix issue38: nicer tracebacks on calls to hooks, particularly early configure/sessionstart ones
• fix missing skip reason/meta information in junitxml files, reported via http://lists.idyll.org/pipermail/testing-in-
python/2011-March/003928.html
• fix issue34: avoid collection failure with “test” prefixed classes deriving from object.
• don’t require zlib (and other libs) for genscript plugin without –genscript actually being used.
• speed up skips (by not doing a full traceback represenation internally)
• fix issue37: avoid invalid characters in junitxml’s output
13.30 v2.0.2
• tackle issue32 - speed up test runs of very quick test functions by reducing the relative overhead
• fix issue30 - extended xfail/skipif handling and improved reporting. If you have a syntax error in your skip/xfail
expressions you now get nice error reports.
Also you can now access module globals from xfail/skipif expressions so that this for example works now:
import pytest
import mymodule
@pytest.mark.skipif("mymodule.__version__[0] == "1")
pass
This will not run the test function if the module’s version string does not start with a “1”. Note that specifying
a string instead of a boolean expressions allows py.test to report meaningful information when summarizing a
test run as to what conditions lead to skipping (or xfail-ing) tests.
• fix issue28 - setup_method and pytest_generate_tests work together The setup_method fixture method now gets
called also for test function invocations generated from the pytest_generate_tests hook.
• fix issue27 - collectonly and keyword-selection (-k) now work together Also, if you do “py.test –collectonly
-q” you now get a flat list of test ids that you can use to paste to the py.test commandline in order to execute a
particular test.
• fix issue25 avoid reported problems with –pdb and python3.2/encodings output
• fix issue23 - tmpdir argument now works on Python3.2 and WindowsXP Starting with Python3.2 os.symlink
may be supported. By requiring a newer py lib version the py.path.local() implementation acknowledges this.
• fixed typos in the docs (thanks Victor Garcia, Brianna Laugher) and particular thanks to Laura Creighton who
also revieved parts of the documentation.
• fix slighly wrong output of verbose progress reporting for classes (thanks Amaury)
• more precise (avoiding of) deprecation warnings for node.Class|Function accesses
• avoid std unittest assertion helper code in tracebacks (thanks Ronny)
13.31 v2.0.1
• refine and unify initial capturing so that it works nicely even if the logging module is used on an early-loaded
conftest.py file or plugin.
13.29. v2.0.3 197

• allow to omit “()” in test ids to allow for uniform test ids as produced by Alfredo’s nice pytest.vim plugin.
• fix issue12 - show plugin versions with “–version” and “–traceconfig” and also document how to add extra
information to reporting test header
• fix issue17 (import-* reporting issue on python3) by requiring py>1.4.0 (1.4.1 is going to include it)
• fix issue10 (numpy arrays truth checking) by refining assertion interpretation in py lib
• fix issue15: make nose compatibility tests compatible with python3 (now that nose-1.0 supports python3)
• remove somewhat surprising “same-conftest” detection because it ignores conftest.py when they appear in sev-
eral subdirs.
• improve assertions (“not in”), thanks Floris Bruynooghe
• improve behaviour/warnings when running on top of “python -OO” (assertions and docstrings are turned off,
leading to potential false positives)
• introduce a pytest_cmdline_processargs(args) hook to allow dynamic computation of command line arguments.
This fixes a regression because py.test prior to 2.0 allowed to set command line options from conftest.py files
which so far pytest-2.0 only allowed from ini-files now.
• fix issue7: assert failures in doctest modules. unexpected failures in doctests will not generally show nicer, i.e.
within the doctest failing context.
• fix issue9: setup/teardown functions for an xfail-marked test will report as xfail if they fail but report as nor-
mally passing (not xpassing) if they succeed. This only is true for “direct” setup/teardown invocations because
teardown_class/ teardown_module cannot closely relate to a single test.
• fix issue14: no logging errors at process exit
• refinements to “collecting” output on non-ttys
• refine internal plugin registration and –traceconfig output
• introduce a mechanism to prevent/unregister plugins from the command line, see
http://pytest.org/plugins.html#cmdunregister
• activate resultlog plugin by default
• fix regression wrt yielded tests which due to the collection-before-running semantics were not setup as with
pytest 1.3.4. Note, however, that the recommended and much cleaner way to do test parametraization remains
the “pytest_generate_tests” mechanism, see the docs.
13.32 v2.0.0
• pytest-2.0 is now its own package and depends on pylib-2.0

• new ability: python -m pytest / python -m pytest.main ability
• new python invcation: pytest.main(args, plugins) to load some custom plugins early.
• try harder to run unittest test suites in a more compatible manner by deferring setup/teardown semantics to the
unittest package. also work harder to run twisted/trial and Django tests which should now basically work by
default.
• introduce a new way to set config options via ini-style files, by default setup.cfg and tox.ini files are searched.
The old ways (certain environment variables, dynamic conftest.py reading is removed).
• add a new “-q” option which decreases verbosity and prints a more nose/unittest-style “dot” output.
• fix issue135 - marks now work with unittest test cases as well

• fix issue126 - introduce py.test.set_trace() to trace execution via PDB during the running of tests even if capturing
is ongoing.
• fix issue123 - new “python -m py.test” invocation for py.test (requires Python 2.5 or above)
• fix issue124 - make reporting more resilient against tests opening files on filedescriptor 1 (stdout).
• fix issue109 - sibling conftest.py files will not be loaded. (and Directory collectors cannot be customized any-
more from a Directory’s conftest.py - this needs to happen at least one level up).
• introduce (customizable) assertion failure representations and enhance output on assertion failures for compar-
isons and other cases (Floris Bruynooghe)
• nose-plugin: pass through type-signature failures in setup/teardown functions instead of not calling them (Ed
Singleton)
• remove py.test.collect.Directory (follows from a major refactoring and simplification of the collection process)
• majorly reduce py.test core code, shift function/python testing to own plugin
• fix issue88 (finding custom test nodes from command line arg)
• refine ‘tmpdir’ creation, will now create basenames better associated with test names (thanks Ronny)
• “xpass” (unexpected pass) tests don’t cause exitcode!=0
• fix issue131 / issue60 - importing doctests in __init__ files used as namespace packages
• fix issue93 stdout/stderr is captured while importing conftest.py
• fix bug: unittest collected functions now also can have “pytestmark” applied at class/module level
• add ability to use “class” level for cached_setup helper
• fix strangeness: mark.* objects are now immutable, create new instances
13.33 v1.3.4
• fix issue111: improve install documentation for windows

• fix issue119: fix custom collectability of __init__.py as a module
• fix issue116: –doctestmodules work with __init__.py files as well
• fix issue115: unify internal exception passthrough/catching/GeneratorExit
• fix issue118: new –tb=native for presenting cpython-standard exceptions
13.34 v1.3.3
• fix issue113: assertion representation problem with triple-quoted strings (and possibly other cases)
• make conftest loading detect that a conftest file with the same content was already loaded, avoids surprises
in nested directory structures which can be produced e.g. by Hudson. It probably removes the need to use
–confcutdir in most cases.
• fix terminal coloring for win32 (thanks Michael Foord for reporting)
• fix weirdness: make terminal width detection work on stdout instead of stdin (thanks Armin Ronacher for
reporting)
• remove trailing whitespace in all py/text distribution files
13.33. v1.3.4 199

13.35 v1.3.2
13.35.1 New features
• fix issue103: introduce py.test.raises as context manager, examples:

with py.test.raises(ZeroDivisionError):
x = 0
1 / x
with py.test.raises(RuntimeError) as excinfo:

call_something()
# you may do extra checks on excinfo.value|type|traceback here
(thanks Ronny Pfannschmidt)

• Funcarg factories can now dynamically apply a marker to a test invocation. This is for example useful if a
factory provides parameters to a test which are expected-to-fail:
def pytest_funcarg__arg(request):
request.applymarker(py.test.mark.xfail(reason="flaky config"))
...
def test_function(arg):
...
• improved error reporting on collection and import errors. This makes use of a more general mechanism, namely
that for custom test item/collect nodes node.repr_failure(excinfo) is now uniformly called so that
you can override it to return a string error representation of your choice which is going to be reported as a (red)
string.
• introduce ‘–junitprefix=STR’ option to prepend a prefix to all reports in the junitxml file.
13.35.2 Bug fixes / Maintenance
• make tests and the pytest_recwarn plugin in particular fully compatible to Python2.7 (if you use the
recwarn funcarg warnings will be enabled so that you can properly check for their existence in a cross-python
manner).
• refine –pdb: ignore xfailed tests, unify its TB-reporting and don’t display failures again at the end.
• fix assertion interpretation with the ** operator (thanks Benjamin Peterson)
• fix issue105 assignment on the same line as a failing assertion (thanks Benjamin Peterson)
• fix issue104 proper escaping for test names in junitxml plugin (thanks anonymous)
• fix issue57 -f|–looponfail to work with xpassing tests (thanks Ronny)
• fix issue92 collectonly reporter and –pastebin (thanks Benjamin Peterson)
• fix py.code.compile(source) to generate unique filenames
• fix assertion re-interp problems on PyPy, by defering code compilation to the (overridable) Frame.eval class.
(thanks Amaury Forgeot)
• fix py.path.local.pyimport() to work with directories
• streamline py.path.local.mkdtemp implementation and usage

• don’t print empty lines when showing junitxml-filename

• add optional boolean ignore_errors parameter to py.path.local.remove
• fix terminal writing on win32/python2.4
• py.process.cmdexec() now tries harder to return properly encoded unicode objects on all python versions
• install plain py.test/py.which scripts also for Jython, this helps to get canonical script paths in virtualenv situa-
tions
• make path.bestrelpath(path) return ”.”, note that when calling X.bestrelpath the assumption is that X is a direc-
tory.
• make initial conftest discovery ignore “–” prefixed arguments
• fix resultlog plugin when used in an multicpu/multihost xdist situation (thanks Jakub Gustak)
• perform distributed testing related reporting in the xdist-plugin rather than having dist-related code in the generic
py.test distribution
• fix homedir detection on Windows
• ship distribute_setup.py version 0.6.13
13.36 v1.3.1
13.36.1 New features
• issue91: introduce new py.test.xfail(reason) helper to imperatively mark a test as expected to fail. Can be used
from within setup and test functions. This is useful especially for parametrized tests when certain configurations
are expected-to-fail. In this case the declarative approach with the @py.test.mark.xfail cannot be used as it
would mark all configurations as xfail.
• issue102: introduce new –maxfail=NUM option to stop test runs after NUM failures. This is a generalization of
the ‘-x’ or ‘–exitfirst’ option which is now equivalent to ‘–maxfail=1’. Both ‘-x’ and ‘–maxfail’ will now also
print a line near the end indicating the Interruption.
• issue89: allow py.test.mark decorators to be used on classes (class decorators were introduced with python2.6)
and also allow to have multiple markers applied at class/module level by specifying a list.
• improve and refine letter reporting in the progress bar: . pass f failed test s skipped tests (reminder: use for
dependency/platform mismatch only) x xfailed test (test that was expected to fail) X xpassed test (test that was
expected to fail but passed)
You can use any combination of ‘fsxX’ with the ‘-r’ extended reporting option. The xfail/xpass results will show
up as skipped tests in the junitxml output - which also fixes issue99.
• make py.test.cmdline.main() return the exitstatus instead of raising SystemExit and also allow it to be called
multiple times. This of course requires that your application and tests are properly teared down and don’t have
global state.
13.36.2 Fixes / Maintenance
• improved traceback presentation: - improved and unified reporting for “–tb=short” option - Errors during test
module imports are much shorter, (using –tb=short style) - raises shows shorter more relevant tracebacks -
–fulltrace now more systematically makes traces longer / inhibits cutting
13.36. v1.3.1 201

• improve support for raises and other dynamically compiled code by manipulating python’s linecache.cache
instead of the previous rather hacky way of creating custom code objects. This makes it seemlessly work on
Jython and PyPy where it previously didn’t.
• fix issue96: make capturing more resilient against Control-C interruptions (involved somewhat substantial refac-
toring to the underlying capturing functionality to avoid race conditions).
• fix chaining of conditional skipif/xfail decorators - so it works now as expected to use multiple
@py.test.mark.skipif(condition) decorators, including specific reporting which of the conditions lead to skip-
ping.
• fix issue95: late-import zlib so that it’s not required for general py.test startup.
• fix issue94: make reporting more robust against bogus source code (and internally be more careful when pre-
senting unexpected byte sequences)
13.37 v1.3.0
• deprecate –report option in favour of a new shorter and easier to remember -r option: it takes a string argument
consisting of any combination of ‘xfsX’ characters. They relate to the single chars you see during the dotted
progress printing and will print an extra line per test at the end of the test run. This extra line indicates the exact
position or test ID that you directly paste to the py.test cmdline in order to re-run a particular test.
• allow external plugins to register new hooks via the new pytest_addhooks(pluginmanager) hook. The new
release of the pytest-xdist plugin for distributed and looponfailing testing requires this feature.
• add a new pytest_ignore_collect(path, config) hook to allow projects and plugins to define exclusion behaviour
for their directory structure - for example you may define in a conftest.py this method:
def pytest_ignore_collect(path):
return path.check(link=1)
to prevent even a collection try of any tests in symlinked dirs.

• new pytest_pycollect_makemodule(path, parent) hook for allowing customization of the Module collection ob-
ject for a matching test module.
• extend and refine xfail mechanism: @py.test.mark.xfail(run=False) do not run the decorated
test @py.test.mark.xfail(reason="...") prints the reason string in xfail summaries specifiying
--runxfail on command line virtually ignores xfail markers
• expose (previously internal) commonly useful methods: py.io.get_terminal_with() -> return terminal width
py.io.ansi_print(...) -> print colored/bold text on linux/win32 py.io.saferepr(obj) -> return limited representation
string
• expose test outcome related exceptions as py.test.skip.Exception, py.test.raises.Exception etc., useful mostly for
plugins doing special outcome interpretation/tweaking
• (issue85) fix junitxml plugin to handle tests with non-ascii output
• fix/refine python3 compatibility (thanks Benjamin Peterson)
• fixes for making the jython/win32 combination work, note however: jython2.5.1/win32 does not provide a
command line launcher, see http://bugs.jython.org/issue1491 . See pylib install documentation for how to work
around.
• fixes for handling of unicode exception values and unprintable objects
• (issue87) fix unboundlocal error in assertionold code
• (issue86) improve documentation for looponfailing

• refine IO capturing: stdin-redirect pseudo-file now has a NOP close() method

• ship distribute_setup.py version 0.6.10
• added links to the new capturelog and coverage plugins
13.38 v1.2.0
• refined usage and options for “py.cleanup”:

py.cleanup # remove "*.pyc" and "*$py.class" (jython) files
py.cleanup -e .swp -e .cache # also remove files with these extensions
py.cleanup -s # remove "build" and "dist" directory next to setup.py files
py.cleanup -d # also remove empty directories
py.cleanup -a # synonym for "-s -d -e 'pip-log.txt'"
py.cleanup -n # dry run, only show what would be removed
• add a new option “py.test –funcargs” which shows available funcargs and their help strings (docstrings on their
respective factory function) for a given test path
• display a short and concise traceback if a funcarg lookup fails
• early-load “conftest.py” files in non-dot first-level sub directories. allows to conveniently keep and access test-
related options in a test subdir and still add command line options.
• fix issue67: new super-short traceback-printing option: “–tb=line” will print a single line for each failing
(python) test indicating its filename, lineno and the failure value
• fix issue78: always call python-level teardown functions even if the according setup failed. This includes
refinements for calling setup_module/class functions which will now only be called once instead of the previous
behaviour where they’d be called multiple times if they raise an exception (including a Skipped exception). Any
exception will be re-corded and associated with all tests in the according module/class scope.
• fix issue63: assume <40 columns to be a bogus terminal width, default to 80
• fix pdb debugging to be in the correct frame on raises-related errors
• update apipkg.py to fix an issue where recursive imports might unnecessarily break importing
• fix plugin links
13.39 v1.1.1
• moved dist/looponfailing from py.test core into a new separately released pytest-xdist plugin.
• new junitxml plugin: –junitxml=path will generate a junit style xml file which is processable e.g. by the Hudson
CI system.
• new option: –genscript=path will generate a standalone py.test script which will not need any libraries installed.
thanks to Ralf Schmitt.
• new option: –ignore will prevent specified path from collection. Can be specified multiple times.
• new option: –confcutdir=dir will make py.test only consider conftest files that are relative to the specified dir.
• new funcarg: “pytestconfig” is the pytest config object for access to command line args and can now be easily
used in a test.
• install ‘py.test’ and py.which with a -$VERSION suffix to disambiguate between Python3, python2.X, Jython
and PyPy installed versions.
13.38. v1.2.0 203

• new “pytestconfig” funcarg allows access to test config object

• new “pytest_report_header” hook can return additional lines to be displayed at the header of a test run.
• (experimental) allow “py.test path::name1::name2::...” for pointing to a test within a test collection directly. This
might eventually evolve as a full substitute to “-k” specifications.
• streamlined plugin loading: order is now as documented in customize.html: setuptools, ENV, commandline,
conftest. also setuptools entry point names are turned to canonical namees (“pytest_*”)
• automatically skip tests that need ‘capfd’ but have no os.dup
• allow pytest_generate_tests to be defined in classes as well
• deprecate usage of ‘disabled’ attribute in favour of pytestmark
• deprecate definition of Directory, Module, Class and Function nodes in conftest.py files. Use pytest collect
hooks instead.
• collection/item node specific runtest/collect hooks are only called exactly on matching conftest.py files, i.e. ones
which are exactly below the filesystem path of an item
• change: the first pytest_collect_directory hook to return something will now prevent further hooks to be called.
• change: figleaf plugin now requires –figleaf to run. Also change its long command line options to be a bit
shorter (see py.test -h).
• change: pytest doctest plugin is now enabled by default and has a new option –doctest-glob to set a pattern for
file matches.
• change: remove internal py._* helper vars, only keep py._pydir
• robustify capturing to survive if custom pytest_runtest_setup code failed and prevented the capturing setup code
from running.
• make py.test.* helpers provided by default plugins visible early - works transparently both for pydoc and for
interactive sessions which will regularly see e.g. py.test.mark and py.test.importorskip.
• simplify internal plugin manager machinery
• simplify internal collection tree by introducing a RootCollector node
• fix assert reinterpreation that sees a call containing “keyword=...”
• fix issue66: invoke pytest_sessionstart and pytest_sessionfinish hooks on slaves during dist-testing, report mod-
ule/session teardown hooks correctly.
• fix issue65: properly handle dist-testing if no execnet/py lib installed remotely.
• skip some install-tests if no execnet is available
• fix docs, fix internal bin/ script generation
13.40 v1.1.0
• introduce automatic plugin registration via ‘pytest11’ entrypoints via setuptools’

pkg_resources.iter_entry_points
• fix py.test dist-testing to work with execnet >= 1.0.0b4
• re-introduce py.test.cmdline.main() for better backward compatibility
• svn paths: fix a bug with path.check(versioned=True) for svn paths, allow ‘%’ in svn paths, make svnwc.update()
default to interactive mode like in 1.0.x and add svnwc.update(interactive=False) to inhibit interaction.

• refine distributed tarball to contain test and no pyc files

• try harder to have deprecation warnings for py.compat.* accesses report a correct location
13.41 v1.0.2
• adjust and improve docs

• remove py.rest tool and internal namespace - it was never really advertised and can still be used with the old
release if needed. If there is interest it could be revived into its own tool i guess.
• fix issue48 and issue59: raise an Error if the module from an imported test file does not seem to come from the
filepath - avoids “same-name” confusion that has been reported repeatedly
• merged Ronny’s nose-compatibility hacks: now nose-style setup_module() and setup() functions are supported
• introduce generalized py.test.mark function marking
• reshuffle / refine command line grouping
• deprecate parser.addgroup in favour of getgroup which creates option group
• add –report command line option that allows to control showing of skipped/xfailed sections
• generalized skipping: a new way to mark python functions with skipif or xfail at function, class and modules
level based on platform or sys-module attributes.
• extend py.test.mark decorator to allow for positional args
• introduce and test “py.cleanup -d” to remove empty directories
• fix issue #59 - robustify unittest test collection
• make bpython/help interaction work by adding an __all__ attribute to ApiModule, cleanup initpkg
• use MIT license for pylib, add some contributors
• remove py.execnet code and substitute all usages with ‘execnet’ proper
• fix issue50 - cached_setup now caches more to expectations for test functions with multiple arguments.
• merge Jarko’s fixes, issue #45 and #46
• add the ability to specify a path for py.lookup to search in
• fix a funcarg cached_setup bug probably only occuring in distributed testing and “module” scope with teardown.
• many fixes and changes for making the code base python3 compatible, many thanks to Benjamin Peterson for
helping with this.
• consolidate builtins implementation to be compatible with >=2.3, add helpers to ease keeping 2 and 3k compat-
ible code
• deprecate py.compat.doctest|subprocess|textwrap|optparse
• deprecate py.magic.autopath, remove py/magic directory
• move pytest assertion handling to py/code and a pytest_assertion plugin, add “–no-assert” option, deprecate
py.magic namespaces in favour of (less) py.code ones.
• consolidate and cleanup py/code classes and files
• cleanup py/misc, move tests to bin-for-dist
• introduce delattr/delitem/delenv methods to py.test’s monkeypatch funcarg
13.41. v1.0.2 205

• consolidate py.log implementation, remove old approach.

• introduce py.io.TextIO and py.io.BytesIO for distinguishing between text/unicode and byte-streams (uses under-
lying standard lib io.* if available)
• make py.unittest_convert helper script available which converts “unittest.py” style files into the simpler
assert/direct-test-classes py.test/nosetests style. The script was written by Laura Creighton.
• simplified internal localpath implementation
13.42 v1.0.2
• fixing packaging issues, triggered by fedora redhat packaging, also added doc, examples and contrib dirs to the
tarball.
• added a documentation link to the new django plugin.
13.43 v1.0.1
• added a ‘pytest_nose’ plugin which handles nose.SkipTest, nose-style function/method/generator

setup/teardown and tries to report functions correctly.
• capturing of unicode writes or encoded strings to sys.stdout/err work better, also terminalwriting was adapted
and somewhat unified between windows and linux.
• improved documentation layout and content a lot
• added a “–help-config” option to show conftest.py / ENV-var names for all longopt cmdline options, and some
special conftest.py variables. renamed ‘conf_capture’ conftest setting to ‘option_capture’ accordingly.
• fix issue #27: better reporting on non-collectable items given on commandline (e.g. pyc files)
• fix issue #33: added –version flag (thanks Benjamin Peterson)
• fix issue #32: adding support for “incomplete” paths to wcpath.status()
• “Test” prefixed classes are not collected by default anymore if they have an __init__ method
• monkeypatch setenv() now accepts a “prepend” parameter
• improved reporting of collection error tracebacks
• simplified multicall mechanism and plugin architecture, renamed some internal methods and argnames
13.44 v1.0.0
• more terse reporting try to show filesystem path relatively to current dir
• improve xfail output a bit
13.45 v1.0.0b9
• cleanly handle and report final teardown of test setup

• fix svn-1.6 compat issue with py.path.svnwc().versioned() (thanks Wouter Vanden Hove)

• setup/teardown or collection problems now show as ERRORs or with big “E“‘s in the progress lines. they are
reported and counted separately.
• dist-testing: properly handle test items that get locally collected but cannot be collected on the remote side -
often due to platform/dependency reasons
• simplified py.test.mark API - see keyword plugin documentation
• integrate better with logging: capturing now by default captures test functions and their immediate
setup/teardown in a single stream
• capsys and capfd funcargs now have a readouterr() and a close() method (underlyingly py.io.StdCapture/FD
objects are used which grew a readouterr() method as well to return snapshots of captured out/err)
• make assert-reinterpretation work better with comparisons not returning bools (reported with numpy from thanks
maciej fijalkowski)
• reworked per-test output capturing into the pytest_iocapture.py plugin and thus removed capturing code from
config object
• item.repr_failure(excinfo) instead of item.repr_failure(excinfo, outerr)
13.46 v1.0.0b8
• pytest_unittest-plugin is now enabled by default

• introduced pytest_keyboardinterrupt hook and refined pytest_sessionfinish hooked, added tests.
• workaround a buggy logging module interaction (“closing already closed files”). Thanks to Sridhar Ratnakumar
for triggering.
• if plugins use “py.test.importorskip” for importing a dependency only a warning will be issued instead of exiting
the testing process.
• many improvements to docs: - refined funcargs doc , use the term “factory” instead of “provider” - added a new
talk/tutorial doc page - better download page - better plugin docstrings - added new plugins page and automatic
doc generation script
• fixed teardown problem related to partially failing funcarg setups (thanks MrTopf for reporting),
“pytest_runtest_teardown” is now always invoked even if the “pytest_runtest_setup” failed.
• tweaked doctest output for docstrings in py modules, thanks Radomir.
13.47 v1.0.0b7
• renamed py.test.xfail back to py.test.mark.xfail to avoid two ways to decorate for xfail
• re-added py.test.mark decorator for setting keywords on functions (it was actually documented so removing it
was not nice)
• remove scope-argument from request.addfinalizer() because request.cached_setup has the scope arg.
TOOWTDI.
• perform setup finalization before reporting failures
• apply modified patches from Andreas Kloeckner to allow test functions to have no func_code (#22) and to make
“-k” and function keywords work (#20)
• apply patch from Daniel Peolzleithner (issue #23)
13.46. v1.0.0b8 207

• resolve issue #18, multiprocessing.Manager() and redirection clash

• make __name__ == “__channelexec__” for remote_exec code
13.48 v1.0.0b3
• plugin classes are removed: one now defines hooks directly in conftest.py or global pytest_*.py files.
• added new pytest_namespace(config) hook that allows to inject helpers directly to the py.test.* namespace.
• documented and refined many hooks
• added new style of generative tests via pytest_generate_tests hook that integrates well with function arguments.
13.49 v1.0.0b1
• introduced new “funcarg” setup method, see doc/test/funcarg.txt

• introduced plugin architecuture and many new py.test plugins, see doc/test/plugins.txt
• teardown_method is now guaranteed to get called after a test method has run.
• new method: py.test.importorskip(mod,minversion) will either import or call py.test.skip()
• completely revised internal py.test architecture
• new py.process.ForkedFunc object allowing to fork execution of a function to a sub process and getting a result
back.
XXX lots of things missing here XXX
13.50 v0.9.2
• refined installation and metadata, created new setup.py, now based on setuptools/ez_setup (thanks to Ralf
Schmitt for his support).
• improved the way of making py.* scripts available in windows environments, they are now added to the Scripts
directory as ”.cmd” files.
• py.path.svnwc.status() now is more complete and uses xml output from the ‘svn’ command if available (Guido
Wesdorp)
• fix for py.path.svn* to work with svn 1.5 (Chris Lamb)
• fix path.relto(otherpath) method on windows to use normcase for checking if a path is relative.
• py.test’s traceback is better parseable from editors (follows the filenames:LINENO: MSG convention) (thanks
to Osmo Salomaa)
• fix to javascript-generation, “py.test –runbrowser” should work more reliably now
• removed previously accidentally added py.test.broken and py.test.notimplemented helpers.
• there now is a py.__version__ attribute

13.51 v0.9.1
This is a fairly complete list of v0.9.1, which can serve as a reference for developers.
• allowing + signs in py.path.svn urls [39106]
• fixed support for Failed exceptions without excinfo in py.test [39340]
• added support for killing processes for Windows (as well as platforms that support os.kill) in py.misc.killproc
[39655]
• added setup/teardown for generative tests to py.test [40702]
• added detection of FAILED TO LOAD MODULE to py.test [40703, 40738, 40739]
• fixed problem with calling .remove() on wcpaths of non-versioned files in py.path [44248]
• fixed some import and inheritance issues in py.test [41480, 44648, 44655]
• fail to run greenlet tests when pypy is available, but without stackless [45294]
• small fixes in rsession tests [45295]
• fixed issue with 2.5 type representations in py.test [45483, 45484]
• made that internal reporting issues displaying is done atomically in py.test [45518]
• made that non-existing files are igored by the py.lookup script [45519]
• improved exception name creation in py.test [45535]
• made that less threads are used in execnet [merge in 45539]
• removed lock required for atomical reporting issue displaying in py.test [45545]
• removed globals from execnet [45541, 45547]
• refactored cleanup mechanics, made that setDaemon is set to 1 to make atexit get called in 2.5 (py.execnet)
[45548]
• fixed bug in joining threads in py.execnet’s servemain [45549]
• refactored py.test.rsession tests to not rely on exact output format anymore [45646]
• using repr() on test outcome [45647]
• added ‘Reason’ classes for py.test.skip() [45648, 45649]
• killed some unnecessary sanity check in py.test.collect [45655]
• avoid using os.tmpfile() in py.io.fdcapture because on Windows it’s only usable by Administrators [45901]
• added support for locking and non-recursive commits to py.path.svnwc [45994]
• locking files in py.execnet to prevent CPython from segfaulting [46010]
• added export() method to py.path.svnurl
• fixed -d -x in py.test [47277]
• fixed argument concatenation problem in py.path.svnwc [49423]
• restore py.test behaviour that it exits with code 1 when there are failures [49974]
• don’t fail on html files that don’t have an accompanying .txt file [50606]
• fixed ‘utestconvert.py < input’ [50645]
• small fix for code indentation in py.code.source [50755]
13.51. v0.9.1 209

• fix _docgen.py documentation building [51285]

• improved checks for source representation of code blocks in py.test [51292]
• added support for passing authentication to py.path.svn* objects [52000, 52001]
• removed sorted() call for py.apigen tests in favour of [].sort() to support Python 2.3 [52481]

INDEX
A configuration value, 28
add() (MarkInfo method), 61 duration (TestReport attribute), 88
add_marker() (Node method), 86
addcall() (Metafunc method), 51 E
addfinalizer() (FixtureRequest method), 24 excinfo (CallInfo attribute), 88
addfinalizer() (Node method), 87 exit() (in module _pytest.runner), 22
addini() (Parser method), 86 extra_keyword_matches (Node attribute), 86
addinivalue_line() (Config method), 85
addoption() (Parser method), 86 F
addopts fail() (in module _pytest.runner), 22
configuration value, 27 fixture() (in module _pytest.python), 23
applymarker() (FixtureRequest method), 24 fixturename (FixtureRequest attribute), 23
args (MarkInfo attribute), 61 FixtureRequest (class in _pytest.python), 23
fromdictargs() (_pytest.config.Config class method), 85
C fspath (FixtureRequest attribute), 23
cached_setup() (FixtureRequest method), 24 fspath (Node attribute), 86
CallInfo (class in _pytest.runner), 87 Function (class in _pytest.python), 87
CallOutcome (class in _pytest.core), 88 function (FixtureRequest attribute), 23
chdir() (monkeypatch method), 56 function (Function attribute), 87
Class (class in _pytest.python), 87
cls (FixtureRequest attribute), 23 G
collect() (Collector method), 87 get_marker() (Node method), 87
Collector (class in _pytest.main), 87 getfuncargvalue() (FixtureRequest method), 24
Collector.CollectError, 87 getgroup() (Parser method), 85
Config (class in _pytest.config), 85 getini() (Config method), 85
config (FixtureRequest attribute), 23 getoption() (Config method), 85
config (Node attribute), 86 getparent() (Node method), 87
configuration value getvalue() (Config method), 85
addopts, 27 getvalueorskip() (Config method), 85
doctest_optionflags, 28
minversion, 27 I
norecursedirs, 27 ihook (Node attribute), 86
python_classes, 27 importorskip() (in module _pytest.runner), 22
python_files, 27 instance (FixtureRequest attribute), 23
python_functions, 27 Item (class in _pytest.main), 87
D K
delattr() (monkeypatch method), 55 keywords (FixtureRequest attribute), 23
delenv() (monkeypatch method), 56 keywords (Node attribute), 86
delitem() (monkeypatch method), 56 keywords (TestReport attribute), 88
deprecated_call() (in module pytest), 22 kwargs (MarkInfo attribute), 61
doctest_optionflags
211
L pytest_exception_interact() (in module

listchain() (Node method), 86 _pytest.hookspec), 81
listextrakeywords() (Node method), 87 pytest_generate_tests() (in module _pytest.hookspec), 81
location (TestReport attribute), 88 pytest_ignore_collect() (in module _pytest.hookspec), 80
longrepr (TestReport attribute), 88 pytest_internalerror() (in module _pytest.hookspec), 81
pytest_itemcollected() (in module _pytest.hookspec), 81
M pytest_keyboard_interrupt() (in module
_pytest.hookspec), 81
main() (in module pytest), 21
pytest_load_initial_conftests() (in module
MarkDecorator (class in _pytest.mark), 60
MarkGenerator (class in _pytest.mark), 60
pytest_namespace() (in module _pytest.hookspec), 79
MarkInfo (class in _pytest.mark), 60
pytest_pycollect_makeitem() (in module
minversion
configuration value, 27
pytest_runtest_call() (in module _pytest.hookspec), 80
Module (class in _pytest.python), 87
pytest_runtest_logreport() (in module _pytest.hookspec),
module (FixtureRequest attribute), 23
81
monkeypatch (class in _pytest.monkeypatch), 55
pytest_runtest_makereport() (in module
N _pytest.hookspec), 80
pytest_runtest_protocol() (in module _pytest.hookspec),
name (MarkInfo attribute), 60 80
name (Node attribute), 86 pytest_runtest_setup() (in module _pytest.hookspec), 80
Node (class in _pytest.main), 86 pytest_runtest_teardown() (in module _pytest.hookspec),
node (FixtureRequest attribute), 23 80
nodeid (Node attribute), 86 pytest_unconfigure() (in module _pytest.hookspec), 80
nodeid (TestReport attribute), 88 Python Enhancement Proposals
norecursedirs PEP 8, 4
configuration value, 27 python_classes
O python_files
option (Config attribute), 85 configuration value, 27
outcome (TestReport attribute), 88 python_functions
P
parametrize() (Metafunc method), 50 R
parent (Node attribute), 86 raiseerror() (FixtureRequest method), 24
Parser (class in _pytest.config), 85 raises() (in module pytest), 21
pluginmanager (Config attribute), 85 repr_failure() (Collector method), 87
pytest_addhooks() (in module _pytest.hookspec), 81 runtest() (Function method), 87
pytest_addoption() (in module _pytest.hookspec), 79
pytest_assertrepr_compare() (in module S
_pytest.hookspec), 30 scope (FixtureRequest attribute), 23
pytest_cmdline_main() (in module _pytest.hookspec), 79 sections (TestReport attribute), 88
pytest_cmdline_parse() (in module _pytest.hookspec), 79 session (FixtureRequest attribute), 24
pytest_cmdline_preparse() (in module _pytest.hookspec), session (Node attribute), 86
79 setattr() (monkeypatch method), 55
pytest_collect_directory() (in module _pytest.hookspec), setenv() (monkeypatch method), 56
80 setitem() (monkeypatch method), 56
pytest_collect_file() (in module _pytest.hookspec), 80 skip() (in module _pytest.runner), 22
pytest_collection_modifyitems() (in module syspath_prepend() (monkeypatch method), 56
pytest_collectreport() (in module _pytest.hookspec), 81 T
pytest_collectstart() (in module _pytest.hookspec), 81
TestReport (class in _pytest.runner), 88
pytest_configure() (in module _pytest.hookspec), 79
pytest_deselected() (in module _pytest.hookspec), 81
212 Index
U
undo() (monkeypatch method), 56
W
warn() (Config method), 85
warn() (Node method), 86
when (CallInfo attribute), 87
when (TestReport attribute), 88
X
xfail() (in module _pytest.skipping), 22
Index 213

Pytest Documentation: Release 2.7.1

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pytest Documentation

holger krekel, trainer and consultant, http://merlinux.eu

May 19, 2015

1 Getting started basics 3

2 pytest reference documentation 21

3 Working with plugins and conftest files 73

4 pytest default plugin reference 77

5 pytest hook reference 79

6 Reference of objects involved in hooks 85

7 List of Third-Party Plugins 89

8 Usages and Examples 93

9 Talks and Tutorials 139

10 Contribution getting started 141

11 pytest-2.3: reasoning for fixture/funcarg evolution 145

12 Release announcements 149

13 Changelog history 181

Download latest version as PDF

GETTING STARTED BASICS

1.1 pytest: helps you write better programs

a mature full-featured Python testing tool

• supports domain-specific Working with non-python tests

1.2 Installation and Getting Started

Pythons: Python 2.6,2.7,3.3,3.4, Jython, PyPy-2.3

To check your installation has installed the correct version:

If you get an error checkout Known Installation issues.

1.2.2 Our first test run

Let’s create a first test file with a simple test function:

That’s it. You can execute the test function now:

4 Chapter 1. Getting started basics

================================= FAILURES =================================

1.2.3 Asserting that a certain exception is raised

Running it with, this time in “quiet” reporting mode:

1.2.4 Grouping multiple tests in a class

1.2. Installation and Getting Started 5

self = <test_class.TestClass object at 0x7fbf54cf5668>

1.2.5 Going functional: requesting a unique temporary directory

6 Chapter 1. Getting started basics

1.2.6 Where to go next

Here are a few suggestions where to go next:

1.2.7 Known Installation issues

easy_install or pip not found?

Install pip for a state of the art python package installer.

py.test not found on Windows despite installation?

1.3 Usage and Invocations

1.3.1 Calling pytest through python -m pytest

New in version 2.0.

1.3. Usage and Invocations 7

1.3.2 Getting help on version, option names, environment variables

py.test --version # shows where pytest was imported from

1.3.3 Stopping after the first (or N) failures

To stop the testing process after the first (N) failures:

1.3.4 Specifying tests / selecting tests

Several test run options:

1.3.5 Modifying Python traceback printing

Examples for modifying traceback printing:

py.test --tb=long # the default informative traceback formatting

1.3.6 Dropping to PDB (Python Debugger) on failures

8 Chapter 1. Getting started basics

1.3.7 Setting a breakpoint / aka set_trace()