[1123581321]

You seem confused about what he was saying. I’m sure you are familiar with unit testing philosophy with your experience. Calling a function and expecting a response does test the behavior of the application, just at a lower level than a request- or multi-request level spec. When he says rewriting a method he is referring to changing the logic of it; a refactor leaves the tests unchanged. That shouldn’t have needed to be spelled out to such a senior developer.

[stouset]

Tests should not generally need to be rewritten unless you’re changing the externally-visible behavior API of a function or library (either the literal API, its effects, or its semantics).

If you’re changing the tests because you’ve changed the internal, non-externally-visible logic of your code, your tests are almost certainly providing you negative value.

Being able to refactor and re-run your existing test suite to ensure consistent behavior is possibly the important property of a good test suite.

[1123581321]

Yes, exactly so.