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.

Target extraction

Implementation files are selected from the execution-log.json (completed_steps[].files_modified.implementation).