Is there an easy way to disable thread parallelism for tests in one file?

[yurivict]

I have a file with several dozen test_xx functions.

They appear to be run in parallel by PyTest, and since one underlying library isn't thread safe - these tests fail intermittently.

One way to fix this is to add thread locking into each of test_xx procedures, but this would be a lot of changes.

Is there a way to set an option instructing PyTest to run these tests sequentially?

[The-Compiler]

pytest doesn't run anything in parallel. There's the pytest-xdist plugin that allows doing so, but that uses processes and not threads.