What Is a Mutation Score Threshold?

A mutation score threshold is a configured minimum for the share of injected code mutations that a test suite catches. Mutation testing deliberately introduces small faults and checks whether tests fail in response; the score is the fraction killed. The threshold fails a build when too many mutations survive undetected.

Why it matters

Mutation score reveals whether tests truly assert behavior, exposing high-coverage suites that never check results. The threshold turns that into an enforceable quality bar, though mutation runs are compute-heavy.

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