How do you tell that your unit tests are correct?

Question

I\'ve only done minor unit testing at various points in my career. Whenever I start diving into it again, it always troubles me how to prove that my tests are correct. How

Answer 1

You can't prove tests are correct, and if you're trying to, you're Doing It Wrong.

Unit tests are a first screen - a smoke test - like all automated testing. They are primarily there to tell you if a change you make later on breaks stuff. They are not designed to be a proof of quality, even at 100% coverage.

The metric does make management feel better, though, and that is useful in itself sometimes!