# Nw Mutation Test

Runs feature-scoped mutation testing to validate test suite quality.

- Repository: https://github.com/nWave-ai/nWave (628 stars)
- Category: Testing
- License: MIT
- Last updated: 2026-09-16
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add nWave-ai/nWave --skill nw-mutation-test -g -a claude-code -y`
Codex: `npx skills add nWave-ai/nWave --skill nw-mutation-test -g -a codex -y`
Cursor: `npx skills add nWave-ai/nWave --skill nw-mutation-test -g -a cursor -y`
Gemini CLI: `npx skills add nWave-ai/nWave --skill nw-mutation-test -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add nWave-ai/nWave`

## Description

Runs feature-scoped mutation testing to validate test suite quality. Use after implementation to verify tests catch real bugs (kill rate >= 80%).

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# 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`).

## Context Files Required

- `docs/feature/{feature-id}/deliver/execution-log.json` - Implementation file extraction
- `scripts/mutation/generate_scoped_configs.py` - Automated config generation (if available)

## Pre-Invocation

Orchestrator performs before delegating:

The rest: https://github.com/nWave-ai/nWave/blob/HEAD/nWave/skills/nw-mutation-test/SKILL.md