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Mutation Testing

Checked
jwilger·vlatest·testing·CC0-1.0

Generates mutation test cases based on code changes to identify weaknesses in unit tests.

Repository

Install on your platform

Showing Claude Code. One command installs this skill into any of the agents below.

  1. 1

    Run this in your project

    terminal
    $ npx skills add jwilger/agent-skills --skill mutation-testing -a claude-code

  2. Uses the open-source skills CLI and needs Node.js. Add -g to install it for your user instead of this project.

What we know about this skill

Publisher

jwilger

Taken from the source listing. We haven't verified who controls this account.

Install target

Live repository

Not pinned. Installing fetches whatever the repository holds at the time you run the command.

No human has reviewed this code. The checks below are a static scan of the files at one commit — nobody has run this skill or judged whether it works. A skill runs with whatever access you give your agent, so read the source before you install it.

Automated safety checks

scanned

This skill passed all 6 checks. We read its files at one commit and looked for the things that make a skill dangerous to run — not for whether it works.

  • Declares what it does: passed

    SKILL.md parses and declares a name and a description.

    SKILL.md exists, its frontmatter parses, and it declares a name and a description.

  • No undeclared network calls: passed

    Makes no network calls.

    Every host the skill dials — from its scripts, its config endpoints or the commands it tells the agent to run — is either well-known package and API infrastructure or declared in its own frontmatter. Links in documentation are not counted.

  • No obfuscated payloads: passed

    No encoded or obfuscated payloads.

    No base64, hex or compressed blob is decoded and then executed, and no encoded shell commands.

  • No credential access: passed

    Reads no keys, tokens, keychains or credential files.

    Neither the code nor the SKILL.md instructions read SSH keys, cloud credentials, keychains, token stores, browser cookie databases or dotfiles that hold secrets.

  • No pipe-to-shell installers: passed

    No pipe-to-shell or download-and-run installers.

    No `curl … | sh` pattern, in the code or in the instructions, that runs code fetched at run time.

  • Pinned to a commit: passed

    Scanned jwilger/agent-skills at e2f5e19add.

    The exact upstream commit SHA that was scanned is recorded, so the result refers to specific bytes.

Commit
e2f5e19add
Manifest
skills/mutation-testing/SKILL.md
Scanned
1 file, 236 lines
This is a static scan, not a review. It reads the skill's files; it does not run them, and it cannot tell you whether the skill is any good or whether the code does what its description says. A skill runs with whatever access you give your agent.
What each check looks for →

About this skill

What it does

This skill enables AI agents to perform mutation testing, a method that validates code quality by introducing small faults into source files and verifying if existing tests detect them. It helps ensure test suites are robust enough to catch real bugs rather than just passing trivially.

When to use it

  • You need to verify that your unit tests actually cover critical logic paths and aren't too permissive.
  • You want to identify weak or redundant tests that fail to catch introduced errors.
  • You are preparing a codebase for high-reliability deployment where test effectiveness is paramount.
  • You aim to automate the detection of "brittle" test suites before they cause production issues.

Key capabilities

  • Automatically injects mutations (faults) into your source code.
  • Executes existing test suites against the mutated code.
  • Reports which tests successfully detect the introduced faults.
  • Highlights tests that fail to catch mutations, indicating gaps in coverage.

Example prompts

  • "Run a mutation testing analysis on my src/utils directory and summarize the results."
  • "Identify specific unit tests that are failing to detect mutations in the authentication module."
  • "Generate a report showing the mutation score for my current test suite."

Tips & gotchas

Mutation testing can be computationally expensive, so it may take longer to run than standard unit tests. Ensure you have sufficient compute resources available before initiating large-scale analysis.