mutation testing Shipped
What this lens looks for
Run mutation testing before claiming tests are complete; platform tools: mutmut (Python), Stryker (TypeScript/JS/.NET), Muter (Swift), Pitest (Kotlin/JVM); examine surviving mutants and write additional tests to kill them
What its verifier checks
Mutation testing run and results reviewed; no surviving mutants in critical paths; mutation score documented or acceptable threshold met before marking test suite complete