1.4 Harms Caused by Defects

SRI KRISHNA COLLEGE OF ENGINEERING AND TECHNOLOGY
Kuniamuthur, Coimbatore, Tamilnadu, India

An Autonomous Institution, Affiliated to Anna University,
Accredited by NAAC with “A” Grade & Accredited by NBA (CSE, ECE, IT, MECH ,EEE, CIVIL& MCT)
SKCET- WEB LEARNING SERIES
Course :18IT926-Software Performance Testing

Module :1
Topic :1.4 Harms Caused by Defects in Software
Faculty :A.M Ratheeshkumar
www.skcet.ac.in
Harms Caused by Defects in S/w
* Software is a tool that we humans use for achieving certain results. It
is like a hammer, a ship, or a car. A defect in software can cause
harm to a person, to the environment or to a company.
* A defect product leads,
* Loss of money
* Loss of time
* Damage to business reputation
* Injury or death
Harms Caused by defects in Software
We have 3 types of Defect Categories:

● Wrong
● Missing
● Extra
Wrong:
⮚ a variation from the given requirement specification.
⮚ This means if there are any discrepancies in requirement
documents it will fall under this category.
Missing:
⮚ Evolved during the development or design phase, when the
customer requirements are missed.
⮚ Occurs when requirements are not noted or understood properly
and delivered to the dev elopers team properly
Extra:
Caused when a requirement is included that is not listed
by a customer.
Basically the defects are classified in to three types:
1.Missing Functionality(Requirement not implemented)

2.Extra Functionality(Added some thing more than need )
3.Wrongly implemented functionality(implemented
requirement is not working)
Distribution of Defects
? Apart from this there is a very big list of defects are
there:
1. incorrect or missing functions,
2. interface errors,
3. errors in data structures or external database access,
4. performance errors, and
5. initialization and termination errors
6. GUI relegated
7.Failure of validation conditions.....etc
Root Causes of Defects:
* The cost of defects can be measured by the impact of the

defects. Earlier found bugs reduce the cost of defect.
* For example, if error is found in the requirement

specifications or in design phase then it can be corrected
and re-issued.
* But if the error is not caught in the specifications and is not

found till the user acceptance then the cost to fix those
errors or defects will be way too expensive.
Impact of Defects
? Starting from Apollo 13
space vehicle many
space missions failed
only due to software
defects
? A serious software glitch
in the F-35 Joint Strike
Fighter air crafts
garnered wide public
attention
Software failure
Impact..(Cntd)
North American Blackout ? Airplane Crash
?A power plant along the American Airlines lost 100

southern shore of Lake million $ in a year due to
Erie, Ohio went offline due error in “Software for
to the high demand which excess booking”.
put the rest of the power
network under greater 300 lives were killed.
stress.
*Software faults can cause death or injury
● radiation treatment kills patients (Therac-25)
● train driver killed
● aircraft crashes
● bank system overdraft letters cause suicide
*In a hospital, a software that keeps track of patient records could

malfunction leading to wrong diagnoses.
Root Causes of Software Defects
Defects and failures basically arise from:
● Errors in the specification, design and implementation of the

software and system
● Errors in use of the system
● Environmental conditions
● Intentional damage
● Potential consequences of earlier errors

* Errors in use of the system or product or application may arise
because of the following reasons:
• Inadequate knowledge of the product or the software to
the tester. The tester may not be aware of the functionalities
of the product and hence while testing the product there
might be some defects or failures.
• Lack of the understanding of the functionalities by the
developer. It may also happen that the developers may not
have understood the functionalities of the product or
application properly. Hence this may result into the defect or
failure.
❑Environmental conditions:
• Failures can also be caused by environmental conditions
as well: for example, a radiation burst, a strong magnetic
field, electronic fields, or pollution could cause faults in
hardware or firmware. Those faults might prevent or
change the execution of software.
❑ Intentional damage
• The defects and failures reported by the testers while
testing the product or the application may arise because of
the intentional damage.
❑ Potential consequences of earlier errors:
• Errors found in the earlier stages of the development

reduce our cost of production. Hence it’s very important
to find the error at the earlier stage. This could be done
by reviewing the specification documents or by
walkthrough. The downward flow of the defect will
increase the cost of production.
Testing and Quality
* Testing helps to measure software quality.
* Testing can find faults; when they are removed, software
quality is improved.
* Testing does for both non-functional attributes and functional
attributes.
* “Quality software is reasonably bug or defect free, delivered

on time and within budget, meets requirements and/or
expectations, and is maintainable”.
* Key aspects of quality for the customer include:
● Good design – looks and style
● Good functionality – it does the job well
● Reliable – acceptable level of breakdowns or failure
● Consistency
● Durable – lasts as long as it should
● Good after sales service
● Value for money

❑Quality Assurance, Quality control and Testing
• Quality Assurance is process oriented and focuses on

defect prevention, while quality control is product
oriented and focuses on defect identification.
• Difference between QA and QC is the heart of

software testing.
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SRI KRISHNA COLLEGE OF ENGINEERING AND TECHNOLOGY

Kuniamuthur, Coimbatore, Tamilnadu, India

SKCET- WEB LEARNING SERIES

Course :18IT926-Software Performance Testing

* A defect product leads,

* Damage to business reputation

We have 3 types of Defect Categories:

1.Missing Functionality(Requirement not implemented)

* The cost of defects can be measured by the impact of the

* For example, if error is found in the requirement

* But if the error is not caught in the specifications and is not

?A power plant along the American Airlines lost 100

*In a hospital, a software that keeps track of patient records could

Defects and failures basically arise from:

● Errors in the specification, design and implementation of the

● Errors in use of the system

● Potential consequences of earlier errors

• Errors found in the earlier stages of the development

* “Quality software is reasonably bug or defect free, delivered

● Good design – looks and style

● Good functionality – it does the job well

● Reliable – acceptable level of breakdowns or failure

● Durable – lasts as long as it should

● Good after sales service

● Value for money

• Quality Assurance is process oriented and focuses on

• Difference between QA and QC is the heart of

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