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Use when evaluating test quality on modules containing business logic, calculation utilities, or state machines to determine whether the tests provide genuine defect detection.
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| name | mutation-testing |
| description | Use when evaluating test quality on modules containing business logic, calculation utilities, or state machines to determine whether the tests provide genuine defect detection. |
| metadata | {"category":"testing","priority":"medium","difficulty":"advanced","estimatedTime":"120","source":"frontendchecklist.io","url":"https://frontendchecklist.io/en/rules/testing/mutation-testing"} |
A codebase can have 90% line coverage and still ship critical bugs if tests only execute code without asserting meaningful outcomes. Mutation testing reveals these gaps by proving that your tests can distinguish correct code from subtly broken code — the standard that actually matters in production.
Assess whether this module has mutation testing configured and whether the mutation score on critical paths meets the project's quality threshold.
Set up Stryker for this module, run an initial mutation report, and improve tests to kill surviving mutants in the critical business logic paths.
Explain what mutation testing is, how Stryker works, and why mutation score is a more meaningful quality signal than code coverage alone.
Review the Stryker configuration and mutation report to identify surviving mutants in critical code paths, and suggest test improvements to kill them.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/en/rules/testing/mutation-testing
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