[ferdterguson]

I struggle with this as well. I wouldn't say I'm very experienced, but I've been around the block for awhile. I use TDD successfully, but I always have problems with edge cases. I think of and try to guard against edge cases, but I feel like testing in practice is really just preventing regressions for test cases. Most the bugs I actually see in my software are of things I didn't think about (obviously).

Sometimes I wonder if I should only write a test when something unexpected happens (e.g. user has a bug report) instead of wasting time writing tests on the front end for core features and obvious edge cases.

I mostly work on scientific software, btw.