tests: thread/stress_heap.py intermittent failure on macOS
The stress_heap.py test was excluded from the macOS CI job with a "is
flaky" comment prior to the analysis period. No direct log observations
are available since it was already excluded, but it's listed in
FLAKY_TESTS restricted to the darwin platform.
PR #18861 now handles this via ignore-on-failure instead of exclusion,
so the test runs and its output is visible but doesn't block CI.
See analysis: https://gist.github.com/andrewleech/5686ed5242e0948d8679c432579e002e
tests: thread/thread_gc1.py intermittent failure on CI
The thread_gc1.py test fails intermittently on CI with False instead of
True. This is the single biggest contributor to CI flakiness on master,
attributed to ~62 of 103 failed runs over 14 months (575 runs sampled).
Observed in settrace_stackless (6 times), coverage (3 times) in a 20-run
window with available logs. The test was already excluded from macos,
qemu_mips, qemu_arm, and qemu_riscv64 jobs prior to PR #18861.
The test spawns threads that perform garbage collection and checks a
boolean result. The failure pattern suggests a race condition in the GC
or thread interaction, not a test logic issue — the test is correctly
detecting a real bug.
Estimated per-execution failure rate: ~1.3% across the 8 CI jobs that
run it.
PR #18861 now ignores this failure in CI so it doesn't block other work,
but the underlying issue should be fixed.
See analysis: https://gist.github.com/andrewleech/5686ed5242e0948d8679c432579e002e