Backend & systems·Testing and test doubles
the test fails one run in twenty, everyone reruns CI until it goes green, and the suite stops meaning anything.
Flaky test
A test that passes and fails without code changes, usually because of timing, ordering, shared state or real network calls. Its real damage is cultural: once reruns are normal, genuine failures get rerun too. Quarantine or delete flaky tests immediately — a test nobody believes is worse than no test.