Summary
Several test classes write to (and rmtree) the shared, cwd-relative default pybnf_output/ output directory. Under pytest -n with enough workers, these collide: one class's teardown rmtree('pybnf_output') runs while another class is mid-fit writing into pybnf_output/..., producing nondeterministic FileNotFoundErrors.
Repro
PYBNF_NO_BNGSIM=1 uv run --no-sync pytest -m "not slow" -n auto
On a 6-core machine (6 workers) this flakes; example failures seen:
FAILED tests/test_seed_determinism.py::TestChainRngSpawn::test_chain_rngs_reseed_on_bootstrap
FAILED tests/test_simplex.py::TestSimplex::test_updates
ERROR tests/test_seed_determinism.py::TestSeedReproducibility::test_mh_seed_reproducibility
FileNotFoundError: '.../pybnf_output/Initialize/parabola_gen_net.net'
The same command on GitHub's hosted runners (4 workers) is reliably green — it's worker-count-sensitive, not a product bug.
Root cause
tests/test_simplex.py — configs default to output_dir = pybnf_output; teardown_class does rmtree('pybnf_output').tests/test_job_class.py — rmtree('pybnf_output', ...) in teardown.tests/test_seed_determinism.py — some configs hit the default pybnf_output/Initialize/ (network-gen) path.
All three share the same relative dir in a shared cwd, so parallel workers race.
Proper fix
Give each test class a unique output dir (e.g. pybnf_output_simplex, pybnf_output_jobclass, …) — or a tmp_path-based one — and update the teardown rmtree + any relative-path assertions accordingly. After that, the local pre-push hook can mirror CI at full -n auto instead of being capped.
Interim mitigation (shipped)
The pre-push pytest-ci-mirror hook is capped at -n 4 (CI's worker count), keeping it in CI's empirically-green regime rather than local -n auto. See .pre-commit-config.yaml.
Summary
Several test classes write to (and
rmtree) the shared, cwd-relative defaultpybnf_output/output directory. Underpytest -nwith enough workers, these collide: one class's teardownrmtree('pybnf_output')runs while another class is mid-fit writing intopybnf_output/..., producing nondeterministicFileNotFoundErrors.Repro
On a 6-core machine (6 workers) this flakes; example failures seen:
The same command on GitHub's hosted runners (4 workers) is reliably green — it's worker-count-sensitive, not a product bug.
Root cause
tests/test_simplex.py— configs default tooutput_dir = pybnf_output;teardown_classdoesrmtree('pybnf_output').tests/test_job_class.py—rmtree('pybnf_output', ...)in teardown.tests/test_seed_determinism.py— some configs hit the defaultpybnf_output/Initialize/(network-gen) path.All three share the same relative dir in a shared cwd, so parallel workers race.
Proper fix
Give each test class a unique output dir (e.g.
pybnf_output_simplex,pybnf_output_jobclass, …) — or atmp_path-based one — and update the teardownrmtree+ any relative-path assertions accordingly. After that, the local pre-push hook can mirror CI at full-n autoinstead of being capped.Interim mitigation (shipped)
The pre-push
pytest-ci-mirrorhook is capped at-n 4(CI's worker count), keeping it in CI's empirically-green regime rather than local-n auto. See.pre-commit-config.yaml.