test(caching): fix flaky BackgroundRevalidationCoordinator tests - #10
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Two tests assumed a fixed delay was enough for a background refresh's finally block to release its key before the next Schedule call — flaky under CI/parallel-test thread-pool contention (observed: 1/369 locally, 368/369 passed). Add BackgroundRevalidationCoordinator.IsScheduled(key), an internal read-only accessor, so tests can poll the actual invariant instead of guessing a timing window. Retrying the Schedule call itself (my first attempt at a fix) was wrong in a more interesting way: Schedule is not idempotent — every successful call starts a new background task — so retrying it inside a polling loop double-counted completions and made the flakiness worse, timing out instead of asserting a wrong number.
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Summary
Found while running the pre-release test suite for v2.2.2:
Schedule_WhenRefreshThrows_ReleasesTheKeyfailed once in an otherwise-clean run (368/369), and repeated stress runs reproduced it inSchedule_AfterPreviousRefreshCompletes_StartsAgaintoo. Both tests, added in PR #8, assumed a fixedTask.Delaywindow was long enough for a background refresh'sfinallyblock to release its key before the test scheduled another one — not reliable under CI/parallel-test thread-pool contention.Changes
BackgroundRevalidationCoordinator.IsScheduled(string key)— new internal, read-only accessor so tests can poll the actual "is this key still claimed" invariant instead of guessing a timing window.WaitUntilAsync), bounded at ~2s, instead of a single fixed sleep.Worth flagging my own mistake along the way: my first attempt at this fix retried the
Schedulecall itself inside the polling loop.Scheduleis not idempotent — every successful call starts a new background task — so retrying it re-triggered work and over-counted completions, which made the test time out instead of failing cleanly. The fix here polls a side-effect-free condition and callsScheduleexactly once per logical step.Verification
--filter FullyQualifiedName~BackgroundRevalidationCoordinator), where the pre-fix version failed within the first handful of runs.dotnet build Stampede.Http.slnx --no-incremental: 0 warnings, 0 errorsNo product code behavior changes —
IsScheduledis additive and test-only in practice, gated behindinternal+ the existingInternalsVisibleTo Stampede.Http.Tests.🤖 Generated with Claude Code