TabNine actually announced that functionality a few weeks ago for their code-completion tool: https://www.tabnine.com/blog/ai-unit-test-generation/

I haven't used it, but it might be what you're looking for. I'm actually pretty sure ChatGPT can write effective tests as well, though.

I've found that chatgpt is pretty OK at writing basic unit tests based upon the code in context. I can even say things like 'please switch to mstest/xunit' and it does the thing like you'd expect.