How to ensure each xdist process gets a different random seed reproducibly?

[l0b0]

I'm working on a project which uses random generators to make sure tests which generate things like database entries don't create duplicates. I've combined this with pytest-randomly and "--randomly-seed=${GITHUB_RUN_ID}" --randomly-dont-reset-seed to have reproducible randomness: if the CI pipeline fails I can easily re-run the exact same thing locally. This is working fine, but when combined with pytest-xdist it looks like each worker is getting the same initial seed, and so the tests are back to generating duplicate values.

Is there some way to send a reproducible but different seed to each test when combined with python-xdist?

[adamchainz]

pytest-randomly goes out of its way to ensure each process gets the same seed, otherwise tests won't be reproducible. The splitting between workers is non-deterministic since it relies on test runtime, which is noisy.

If you need to ensure different database records are created from different processes, you can use os.getpid() for a different number in each process. This could be used in a hash or as a seed to a local Random() instance (which pytest-randomly won't affect)