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Agent skill

Mutation Test

by nwiizo in nwiizo/ccswarm

Run mutation tests with cargo-mutants to verify test quality.

MITAuto-check passedDevelopment

Install Mutation Test

skills CLI
$ npx skills add nwiizo/ccswarm --skill mutation-test -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install nwiizo/ccswarm mutation-test --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/nwiizo/ccswarm.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/mutation-test .claude/skills/mutation-test && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
mutation-test
GitHub stars
153
Token cost
~189 tokens
SKILL.md length
21 words
Files
1
Skills in repo
12
Repo updated
First seen
Licence
MIT

At a glance

Run mutation tests with cargo-mutants to verify test quality.

  • Development work in your project
  • Calls cargo

What it does

Mutation Test is an agent skill from nwiizo/ccswarm. Run mutation tests with cargo-mutants to verify test quality. Reports caught, missed, and timed-out mutants.

Its SKILL.md is about 190 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Development. The repository describes itself as: Multi-agent orchestration system using Claude Code with Git worktree isolation and specialized AI agents for collaborative development. The licence is MIT.

When your agent uses it

  • Development work in your project

Example prompts

  • “/mutation-test”

What it can do on your machine

Read from SKILL.md and the folder at commit 1cec7fe. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • cargo

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Mutation Test loads about 189 tokens when it runs. Until then it costs about 31 tokens; SKILL.md has 21 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~31
When it runs · the whole SKILL.md, loaded when a task matches
~189

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from nwiizo/ccswarm at commit 1cec7fe, republished under its MIT licence (© nwiizo). 21 words, ~189 tokens.

Download SKILL.mdSave it as .claude/skills/mutation-test/SKILL.md (or your agent's skills folder).
name
mutation-test
description
Run mutation tests with cargo-mutants to verify test quality. Reports caught, missed, and timed-out mutants.
user-invocable
true
argument-hint
[crate-name]

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.

© nwiizo, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .agents/skills/mutation-test of nwiizo/ccswarm.

Open the folder on GitHubat commit 1cec7fe

Compare with similar skills

Mutation Test next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Mutation Test compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Mutation Test this skillnwiizo/ccswarm153—~189Automated safety check: PassMIT
Vercel Composition Patternssupabase/supabase111k59 repos~726Automated safety check: PassMIT
Finishing a Development Branchobra/superpowers296k5 repos~1.9kAutomated safety check: PassMIT
Typescript Advanced Typesrolling-scopes/rsschool-app10k25 repos~4.2kAutomated safety check: PassMPL-2.0
PR Babysitteropeninterpreter/openinterpreter69k3 repos~4.2kAutomated safety check: PassApache-2.0
Code Review ChecklistshareAI-lab/learn-claude-code78k5 repos~1.1kAutomated safety check: PassMIT

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Categories

Questions about Mutation Test

What does Mutation Test do?

Run mutation tests with cargo-mutants to verify test quality. Mutation Test is an agent skill from nwiizo/ccswarm. Run mutation tests with cargo-mutants to verify test quality.

When should I use Mutation Test?

Mutation Test fits situations like: development work in your project.

How do I install Mutation Test in Claude Code?

Run `npx skills add nwiizo/ccswarm --skill mutation-test -a claude-code`. Or copy the skill folder (.agents/skills/mutation-test in nwiizo/ccswarm) into .claude/skills/mutation-test in your project. Claude Code loads it when a task matches its description.

How do I install Mutation Test in Codex?

Run `npx skills add nwiizo/ccswarm --skill mutation-test -a codex`. Or copy the skill folder (.agents/skills/mutation-test in nwiizo/ccswarm) into .agents/skills/mutation-test in your project. Codex loads it when a task matches its description.

Can I use Mutation Test in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add nwiizo/ccswarm --skill mutation-test -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/mutation-test, .gemini/skills/mutation-test, .github/skills/mutation-test and .opencode/skills/mutation-test in your project.

What does Mutation Test need to run?

Going by SKILL.md and its folder, Mutation Test needs the command-line tools its instructions call (cargo).

Does Mutation Test access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Mutation Test safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Mutation Test use?

Mutation Test is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Mutation Test use?

About 189 tokens (SKILL.md is roughly 756 characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Mutation Test?

Skills that share tags, products or a category with Mutation Test: Vercel Composition Patterns (supabase/supabase, 111k stars), Finishing a Development Branch (obra/superpowers, 296k stars), Typescript Advanced Types (rolling-scopes/rsschool-app, 10k stars) and PR Babysitter (openinterpreter/openinterpreter, 69k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Mutation Test?

nwiizo (a GitHub user) maintains it in nwiizo/ccswarm, which has 153 GitHub stars. The repository holds 12 skills in this directory. The repository was last updated on September 14, 2026.

Source: nwiizo/ccswarm on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.