Tests run x2.3 faster (locally): 18s VS 42s.

The drawback is that it's easy to introduce race condition. We need to be careful and mark tests that modify files in working directory with @workdir_lock decorator introduced in this PR.

To make it easier to debug race conditions, I added pytest-timeout plugin.

Stress-tested with -n 50 - adjusted pytest timeout as a result (5 -> 20).
After all adjustments, 10 runs passed ✅

Note: I added test-cov.sh script and moved --cov --cov-context=test to it. This way when we run just test.sh it works much faster (doesn't store coverage data).

Inline snapshot gives the following:

INFO: inline-snapshot was disabled because you used xdist. This means that tests with snapshots will continue to run, but snapshot(x) will only return x and inline-snapshot will not be able to fix snapshots or generate reports.

To update inline snapshots we can run tests as bash scripts/test.sh -n 0