I've actually found a lot of success with the opposite where I write the code and AI writes the unittests. I would have otherwise written a few unit tests, but AI makes typically 20x that many. Since my code is already documented, it can get lots of good context. I typically instruct it to check the branch's diff relative to main and test only those changes. I might skim them over, delete some that don't make sense in context and would never pass, and update one or two. Typically after a few rounds of iteration, I have tons of tests I would never have written on my own, and a human-made feature.