Rust TDD Workflow
rtk-ai/rtk
Enforces red-green-refactor for Rust work, with idiomatic test patterns, a naming convention and a pre-commit gate of cargo fmt, clippy and test.
Run cargo-mutants on selected Rust code and investigate gaps in tests revealed by surviving mutations.
Install Mutants
$ npx skills add nwiizo/cargo-coupling --skill mutants -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install nwiizo/cargo-coupling mutants --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/nwiizo/cargo-coupling.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.claude/skills/mutants .claude/skills/mutants && rm -rf skills-srcUse ~/.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/
Install the "mutants" agent skill from https://github.com/nwiizo/cargo-coupling/tree/main/.claude/skills/mutants into .claude/skills/mutants/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mutants", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/nwiizo/cargo-coupling/tree/main/.claude/skills/mutantsType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add nwiizo/cargo-coupling --skill mutants -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install nwiizo/cargo-coupling mutants --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/nwiizo/cargo-coupling.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.claude/skills/mutants .agents/skills/mutants && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "mutants" agent skill from https://github.com/nwiizo/cargo-coupling/tree/main/.claude/skills/mutants into .agents/skills/mutants/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mutants", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add nwiizo/cargo-coupling --skill mutants -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install nwiizo/cargo-coupling mutants --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/nwiizo/cargo-coupling.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.claude/skills/mutants .cursor/skills/mutants && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "mutants" agent skill from https://github.com/nwiizo/cargo-coupling/tree/main/.claude/skills/mutants into .cursor/skills/mutants/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mutants", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/nwiizo/cargo-coupling.git --path .claude/skills/mutants--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add nwiizo/cargo-coupling --skill mutants -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install nwiizo/cargo-coupling mutants --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/nwiizo/cargo-coupling.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.claude/skills/mutants .gemini/skills/mutants && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "mutants" agent skill from https://github.com/nwiizo/cargo-coupling/tree/main/.claude/skills/mutants into .gemini/skills/mutants/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mutants", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install nwiizo/cargo-coupling mutantsInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add nwiizo/cargo-coupling --skill mutants -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/nwiizo/cargo-coupling.git skills-src && mkdir -p .github/skills && cp -r skills-src/.claude/skills/mutants .github/skills/mutants && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "mutants" agent skill from https://github.com/nwiizo/cargo-coupling/tree/main/.claude/skills/mutants into .github/skills/mutants/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mutants", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add nwiizo/cargo-coupling --skill mutants -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install nwiizo/cargo-coupling mutants --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/nwiizo/cargo-coupling.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.claude/skills/mutants .opencode/skills/mutants && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "mutants" agent skill from https://github.com/nwiizo/cargo-coupling/tree/main/.claude/skills/mutants into .opencode/skills/mutants/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mutants", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
mutants- GitHub stars
- 111
- Token cost
- ~414 tokens
- SKILL.md length
- 170 words
- Files
- 1
- Skills in repo
- 12
- Repo updated
- First seen
- Licence
- MIT
At a glance
Run cargo-mutants on selected Rust code and investigate gaps in tests revealed by surviving mutations.
- Testing & QA work in your project
- Calls cargo
What it does
Mutants is an agent skill from nwiizo/cargo-coupling. Run cargo-mutants on selected Rust code and investigate gaps in tests revealed by surviving mutations.
Its SKILL.md is about 410 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 Testing & QA. It works with Rust. The repository describes itself as: A coupling analysis tool for Rust projects - measuring the 'right distance' in your code. The licence is MIT.
When your agent uses it
- Testing & QA work in your project
Example prompts
- “/mutants”
Requirements
- Pre-approved tools (allowed-tools): Bash, Read, Grep, Glob, Edit
What it can do on your machine
Read from SKILL.md and the folder at commit aa0d18b. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves these tools, so the agent can use them without asking each time:
BashReadGrepGlobEdit
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
Mutants loads about 414 tokens when it runs. Until then it costs about 28 tokens; SKILL.md has 170 words of instructions outside code blocks.
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: notes
The automated check noted patterns worth knowing about, such as sudo or a known installer.
- NotePre-approves every shell command (allowed-tools: Bash)SKILL.md
allowed-tools: Bash, Read, Grep, Glob, Edit
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/cargo-coupling at commit aa0d18b, republished under its MIT licence (© nwiizo). 170 words, ~414 tokens.
Download SKILL.mdSave it as
.claude/skills/mutants/SKILL.md (or your agent's skills folder).- name
- mutants
- description
- Run cargo-mutants on selected Rust code and investigate gaps in tests revealed by surviving mutations.
- allowed-tools
- Bash, Read, Grep, Glob, Edit
- argument-hint
- [-f FILE] [-F FUNCTION]
- user-invocable
- true
Mutation Testing
Run the requested scope, or start with the changed files. A full-project run is appropriate when requested; mutation testing is not a default release requirement.
rtk proxy cargo mutants --no-shuffle -f src/config.rs
rtk proxy cargo mutants --no-shuffle -F 'function_name'Use cargo mutants --help for installed options and job limits. Inspect the actual
run output and mutants.out/missed.txt to distinguish outcomes:
| Result | Interpretation |
|---|---|
| caught | Tests detected the mutation |
| missed | Tests did not detect it; inspect reachability and observable behavior |
| unviable | The mutated program did not compile |
| timeout | Execution exceeded its limit; investigate before assigning a cause |
Prioritize changed business behavior and actionable gaps. Existing misses may be relevant to the requested scope; do not dismiss CLI or output behavior solely by filename. Some surviving mutations preserve behavior or cannot be meaningfully exercised, so zero missed mutants is not a universal completion criterion.
For diagnosis, report actionable misses and unresolved cases with evidence. When test improvements are requested, add assertions for observable behavior, run the affected tests, and rerun the relevant mutations. Complete with caught/missed/ unviable/timeout results for the tested scope and explain remaining limitations.
© 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 .claude/skills/mutants of nwiizo/cargo-coupling.
Open the folder on GitHubat commit aa0d18b
Compare with similar skills
Mutants 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.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Mutants this skillnwiizo/cargo-coupling | 111 | — | ~414 | Automated safety check: Notes | MIT | |
| Rust TDD Workflowrtk-ai/rtk | 83k | — | ~753 | Automated safety check: Notes | Apache-2.0 | |
| Remote Executor Integration Testsopeninterpreter/openinterpreter | 69k | 2 repos | ~842 | Automated safety check: Pass | Apache-2.0 | |
| Apple Container Test RunnerRustPython/RustPython | 22k | — | ~467 | Automated safety check: Pass | MIT | |
| RTK Filter TDD in Rustrtk-ai/rtk | 83k | — | ~1.9k | Automated safety check: Notes | Apache-2.0 | |
| OpenLogi Device Fixture ContributionAprilNEA/OpenLogi | 23k | — | ~1.2k | Automated safety check: Pass | Apache-2.0 |
Similar skills
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Apple Container Test Runner
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Runs RustPython tests inside a Linux container built with Apple's container CLI, so macOS users can compare Linux results with their local ones.
RTK Filter TDD in Rust
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Enforces red-green-refactor for new RTK output filters in Rust, using real captured fixtures, snapshot tests with insta and token-savings assertions.
OpenLogi Device Fixture Contribution
AprilNEA/OpenLogi
Guides recording, privacy review and offline verification of OpenLogi device fixtures with the fixture contribute and verify commands, without treating replay as proof of hardware behavior.
GreptimeDB Fuzz CI Failure Investigation
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Diagnoses a failed GreptimeDB fuzz CI job by pulling its GitHub Actions logs and fuzz artifacts, then matching the evidence to the local source code.
More from nwiizo/cargo-coupling
All 12 skills in this repoBalanced Coupling
nwiizo/cargo-coupling
Interpret cargo-coupling findings using Khononov's strength, distance, and volatility model.
Cargo Coupling
nwiizo/cargo-coupling
Explain cargo-coupling CLI options and .coupling.toml configuration.
Release
nwiizo/cargo-coupling
Prepare or publish a cargo-coupling version when the user requests a release.
Analyze
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Run cargo-coupling and interpret a Rust project's coupling report, history, or baseline diff.
Check Balance
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Check a Rust project's coupling health summary or run a requested CI quality gate.
Hotspots
nwiizo/cargo-coupling
Rank a Rust project's refactoring candidates using cargo-coupling hotspot results.
Related
Works with
Categories
Questions about Mutants
What does Mutants do?
Run cargo-mutants on selected Rust code and investigate gaps in tests revealed by surviving mutations. Mutants is an agent skill from nwiizo/cargo-coupling. Run cargo-mutants on selected Rust code and investigate gaps in tests revealed by surviving mutations.
When should I use Mutants?
Mutants fits situations like: testing & QA work in your project.
How do I install Mutants in Claude Code?
Run `npx skills add nwiizo/cargo-coupling --skill mutants -a claude-code`. Or copy the skill folder (.claude/skills/mutants in nwiizo/cargo-coupling) into .claude/skills/mutants in your project. Claude Code loads it when a task matches its description.
How do I install Mutants in Codex?
Run `npx skills add nwiizo/cargo-coupling --skill mutants -a codex`. Or copy the skill folder (.claude/skills/mutants in nwiizo/cargo-coupling) into .agents/skills/mutants in your project. Codex loads it when a task matches its description.
Can I use Mutants 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/cargo-coupling --skill mutants -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/mutants, .gemini/skills/mutants, .github/skills/mutants and .opencode/skills/mutants in your project.
What does Mutants need to run?
Going by SKILL.md and its folder, Mutants needs the command-line tools its instructions call (cargo). Its frontmatter pre-approves these tools: Bash, Read, Grep, Glob, Edit.
Does Mutants 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 Mutants safe to install?
Our automated static check of SKILL.md found notes only (pre-approves every shell command (allowed-tools: bash)), nothing it rates as a warning. It is not a guarantee. Review the folder before installing.
What licence does Mutants use?
Mutants 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 Mutants use?
About 414 tokens (SKILL.md is roughly 1.7k 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 Mutants?
Skills that share tags, products or a category with Mutants: Rust TDD Workflow (rtk-ai/rtk, 83k stars), Remote Executor Integration Tests (openinterpreter/openinterpreter, 69k stars), Apple Container Test Runner (RustPython/RustPython, 22k stars) and RTK Filter TDD in Rust (rtk-ai/rtk, 83k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Mutants?
nwiizo (a GitHub user) maintains it in nwiizo/cargo-coupling, which has 111 GitHub stars. The repository holds 12 skills in this directory. The repository was last updated on October 8, 2026.
Source: nwiizo/cargo-coupling on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.