deflake

Deflake a flaky test

A deflake: issue names ONE test that has been observed failing and then passing on a rerun of the same commit — the definitive flaky signature. Your job is to make that test deterministic without changing what it verifies.

The issue body carries the test identity (file + name) and the observed failure signature (e.g. Test timed out in 5000ms, Timed out waiting for …, an order-dependent assertion, a wall-clock/random-dependent value). Read the test, reproduce the mechanism in your head, and apply the SMALLEST fix from the allowed set below that removes the nondeterminism.

The only allowed fixes

1. Raise a timeout / poll budget. A test that blows vitest's default under CI contention (fully-mocked or I/O-bound, not a perf test) gets a generous per-test testTimeout (3rd arg to it), or its internal poll loop is given a real wall-clock budget instead of a fixed iteration count (a fixed count of setImmediate turns elapses in milliseconds and races real I/O).
2. Stabilize timing / waiting. Replace a bare setTimeout/fixed sleep with an explicit await of the real condition (vi.waitFor, a resolved promise, an event). Pre-warm a lazy load (e.g. a WASM runtime) in beforeAll so per-test time doesn't include first-load cost.
3. Make randomness / time deterministic. Seed the RNG, vi.useFakeTimers() / mock Date.now, or pin the input so a value that depends on the real clock or Math.random can't drift.
4. Isolate / serialize interference. Give tests that collide on a shared resource (a same-named tempdir, a fixed port, a global singleton) unique per-test resources, or serialize them.

Hard rules

• Never delete the test, skip/todo it, loosen an assertion, widen an expected range, add a blanket try/catch, or add a retry wrapper around the assertion. Those hide the flake instead of fixing it — and could hide a real bug. If none of the four fixes applies, or the failure looks like a REAL intermittent product bug (not test nondeterminism), write <workdir>/failure.md explaining what you found and stop. A human deflakes it.
• Keep the diff minimal and local to the named test (and its file's helpers). Do not refactor unrelated code.
• Preserve every assertion and every input exactly. A timeout bump changes only the ceiling; a determinism fix changes only the source of nondeterminism.
• Prefer a per-test or per-file change over a global config change unless the same class demonstrably spans the whole package (then a testTimeout in that package's vitest.config.ts is acceptable, as it only raises the ceiling and weakens no assertion).