| name | nw-mutation-test |
| description | Runs feature-scoped mutation testing to validate test suite quality. Use after implementation to verify tests catch real bugs (kill rate >= 80%). |
| user-invocable | true |
| argument-hint | [feature-id] - Optional: --threshold=[75|80|85] --language=[auto|python|java|javascript] |
NW-MUTATION-TEST: Feature-Scoped Mutation Testing
Wave: QUALITY_GATE
Agent: Crafter (nw-software-crafter)
Overview
Run mutation testing against implementation files from the current feature. Extracts targets from the execution-log.json (see Target extraction)|generates feature-scoped configs|delegates to software-crafter. Uses cosmic-ray (Python)|PIT (Java)|Stryker (JS/TS/C#).
Mutation Testing Strategy
Projects declare a strategy via ## Mutation Testing Strategy in CLAUDE.md: per-feature | nightly-delta | pre-release | disabled.
Default (when unspecified): nightly-delta — the recommended mode. CI runs mutmut nightly against modules changed since the last run (the delta), keeping per-feature delivery gates fast. /nw-mutation-test performs an explicit, on-demand feature-scoped run regardless of strategy; under nightly-delta the in-wave Phase 5 gate is skipped and the work is handled by the CI nightly pipeline.
