Would you be open to a PR to add verifying stub_const? eg:

class User
  OFFER_VALUE = 3
end

# spec tests ->

it "reads the value" do
  stub_const_verifying("User::OFFER_VALUATION", 4)
  # -> ArgumentError:
  Cannot stub constant User::OFFER_VALUATION because it is not defined
end

Rational

We strongly favour a fail-fast startup in our apps.

eg, we use this to ensure our ENV is all correct before proceeding with app boot proper:

class User
  OFFER_VALUE = `ENV.fetch("OFFER_VALUE")`
end

If we then want to test various different states of ENV, we need to stub const, but if the const name is mistyped, we get no feedback.

Adding this as a new method would be trivial. Would you like a PR for it?

Maybe there could be an rspec config which says "the standard stub_const is now verifying, wherever used"

Any ideas or suggestions gratefully received!