On: 5% of 666 Python repos had comma typo bugs (inc V8...

[geofft]

The errors were usually in tests themselves. Are you arguing that tests need their own tests to test that they are testing the right thing? Usually I think people believe that tests do not need to be tested and should not be tested, i.e., that you measure "100% coverage" against non-test code alone.

[samhw → geofft]

I don't think anyone could disagree: you could never exceed 0% code coverage if your definition was recursive (i.e. included tests, tests-of-tests, tests-of-tests-of-tests, ...).

[Cpoll → samhw]

Only if you generate infinite tests, then your coverage approaches 0%. But 100% covered code + 0% covered tests = ~50% total coverage.

Also, the obvious solution is self-testing code. (Jokes aside, structures like code contracts attempt something like this).