mutation-test-runner

Line coverage measures execution, not assertion correctness, allowing AI-generated tests with tautological assertions to achieve >90% coverage. Mutation testing exposes this false confidence by introducing code mutations and verifying that existing tests detect the altered behavior, often revealing <40% mutation scores in such suites.

You can run mutation testing in a PR-level incremental mode scoped to changed code to avoid slow full sweeps on every pull request. This targets specific critical access control paths while scheduling nightly full mutation sweeps for release-bound modules to enforce quality gates.

Yes, mutation testing supports Python and C++ through mutmut, Cosmic Ray, and mull, alongside Stryker, PIT, and cargo-mutants. It integrates into CI/CD pipelines to enforce configurable mutation score thresholds across JavaScript, TypeScript, C#, Java, Kotlin, C, C++, and Rust.

Mutation testing tracks regression by alerting on mutation score drops exceeding 5 percentage points against baseline runs. This catches silent test quality degradation in critical modules like payment processing, blocking releases when scores fall below enforced minimum thresholds.

Yes, you can configure CI/CD quality gates to enforce minimum mutation score thresholds for critical code paths like refund processing. The pipeline blocks the release if the mutation score falls below the 75% threshold and surfaces surviving mutants on access control paths.

Mutation testing is the best way to validate real bug detection by introducing small, targeted code mutations and verifying that existing tests fail. This eliminates the false confidence of line coverage metrics alone and ensures tests actually assert on correct behavior.