I work in Python as well and find Claude quite poor at writing proper tests, might be using it wrong. Just last week, I asked Opus to create a small integration test (with pre-existing examples) and it tried to create a 200-line file with 20 tests I didn't ask for.

I am not sure why, but it kept trying to do that, although I made several attempts.

Ended up writing it on my own, very odd. This was in Cursor, however.