If you use standard unittest discovery the third item might apply as well, though probably not to the same degree.

I don’t think unittest has any support for distribution so the xdist stuff is a no.

On the other hand you could use unit test as the API with Pytest as your test runner. Then you can also use xdist. And eventually migrate to the Pytest test api because it’s so much better.

So, I'd run the tests under cProfile first.

Another thing that can slow down pytest collection and bootstrap is how fixture are loaded. So reducing number or scope of fixtures may help too.

I don't disagree that it's "complex, informally specified" (idk about bug ridden or silencing critics), but it's just silly to say it only survives because of AI. It was a top-used language before AI got big for web development, data science and all sorts of scientific analysis, and these haven't gone away: I don't expect Python lost much ground in these fields, if any.