I don't know whether this is a documentation problem or a bug, but it looks like no coverage data is saved for daemon threads. Specifically, I'm using pytest-cov, which seems to start coverage with auto_data=True. Presumably coverage never writes any data because the thread never terminates, although it's possible I'm way off-base in my understanding of what's happening.
If I'm not completely misunderstanding the problem, then it seems like this is at least something that would be appropriate to put into the documentation, ideally with some sort of workaround. Unfortunately, this may just be an impossible situation with no general solution.
Anyway, I thought I should bring this up, and hopefully I might be able to find a solution in my particular application. Thank you for your great work on coverage, and I hope I haven't completely misunderstood the problem I'm seeing. Thanks.