pytest-xdist test fixes

With two workers and a restart limit of three, the fourth worker crash requests shutdown while another test can still be running. That test may also crash. The original queued-work test requires exactly four failures, even though five failures can occur without exceeding the replacement limit.

Scope and behavior

concurrent-worker-crashes.patch changes the assertions in TestNodeFailure.test_max_worker_restart_tests_queued in testing/acceptance_test.py. It requires exactly three replacements, four or five failed tests, the failed-tests exit status, the limit message, and no internal error. It retains the two-worker workload and ten queued tests.

worker-startup-timeout.patch changes the remote-test helper's event timeout from 10 to 60 seconds so loaded builders have time to start workers. The helper returns immediately when an event arrives and still has a bounded wait.

The existing nixpkgs pytest-9 compatibility patches remain in place. Production scheduling and worker-restart behavior are unchanged.

Reproduction and focused checks

Use a disposable pytest-xdist 3.8.0 checkout with its test dependencies and the nixpkgs pytest-9 compatibility patches where required. From this directory:

patch --fuzz=0 -d /path/to/pytest-xdist -p1 < concurrent-worker-crashes.patch
patch --fuzz=0 -d /path/to/pytest-xdist -p1 < worker-startup-timeout.patch
cd /path/to/pytest-xdist
python -m pytest testing/acceptance_test.py \
  -k test_max_worker_restart_tests_queued -q
python -m pytest testing/test_remote.py -q

Twenty unmodified runs passed during the review. To force the failing schedule, modify the generated crashing test in a disposable checkout to accept worker_id: make gw3 wait for a marker created by gw4, and make gw4 pause 0.1 seconds after creating the marker. Then both have in-flight tests when shutdown starts. Bound the marker wait so a reproduction failure cannot hang the suite. The original assertion fails on five reported failures; the patched test passes.

Worker startup and outer concurrency

default.nix runs the outer suite with one worker to limit nested process pools. This is a Nix test-runner setting; the source timeout change lives in worker-startup-timeout.patch.

A separate reproduction inserts an 11-second pytest_sessionstart delay into the child created by test_basic_collect_and_runtests in testing/test_remote.py. The original 10-second channel wait fails; the 60-second wait passes. This bounds waits for test worker events, including startup, rather than changing a product deadline.

Upstream status

These are standalone test patches for pytest-xdist 3.8.0. No upstream submission was made during this work. Recheck the allowed in-flight failures, replacement count, and remote-test wait when updating the scheduler or worker behavior.

Local NixOS integration and build results

../default.nix loads default.nix through pythonPackagesExtensions. From the repository root:

nix build --no-link -L .#nixosConfigurations.jeeves.pkgs.python314Packages.pytest-xdist

After consolidating the settings in this directory, the full x86-64-v3 package build passed 185 tests, with 6 existing skips and 10 expected failures. Nix evaluation confirmed the same outer-worker limit and preserved existing patches, with the timeout now applied as a source patch.

The earlier forced concurrent-crash and delayed-startup reproductions passed after their fixes; the focused crash test also passed after formatting its assertion.

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