# Mutation Test

> Run mutation tests with cargo-mutants to verify test quality. Reports caught, missed, and timed-out mutants.

- Skill: `nwiizo/mutation-test` (Agent Skill)
- Install (CLI): `npx skillmds@latest add nwiizo/mutation-test`
- Raw SKILL.md: https://api.skillmd.com/api/skills/nwiizo/mutation-test/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: nwiizo (https://skillmd.com/u/nwiizo)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/nwiizo/mutation-test

---


Run mutation tests on the specified crate (default: ccswarm):

```bash
# Install if needed
cargo mutants --version || cargo install cargo-mutants

# List mutants
cargo mutants --list -p $ARGUMENTS | head -50

# Run mutation tests
cargo mutants -p ${1:-ccswarm} --timeout 120 -j 4

# Report results
echo "=== Caught ===" && wc -l mutants.out/caught.txt
echo "=== Missed ===" && cat mutants.out/missed.txt
echo "=== Timeout ===" && wc -l mutants.out/timeout.txt
```

Focus on `missed` mutants in business logic - these indicate insufficient test coverage.