How is mutation testing different from code coverage?

While coverage only measures which lines were executed, mutation testing measures if the tests would actually fail if bugs were introduced, providing a more accurate metric for test quality.

What are zombie tests?

Zombie tests are tests that run and pass but don't actually validate the logic correctly, meaning they would still pass even if the underlying code was broken or mutated.

Will this skill modify my source code?

No, the skill uses isolated git worktrees for mutations, ensuring your main working tree remains untouched. It only applies refactoring changes after your explicit approval.

Is mutation testing slow?

This skill uses parallel execution and offers different modes (Quick, Standard, Deep) to provide feedback in as little as 1-2 minutes for focused files, significantly faster than traditional sequential tools.

Mutation Testing Auditor

Name: Mutation Testing Auditor
Author: citadelgrad

bycitadelgrad

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Security & Testing

Audits test suite quality by injecting semantic code mutations to identify zombie tests and automate test suite refactoring.

The Mutation Testing Skill provides a rigorous alternative to traditional code coverage by measuring how effectively your tests actually catch bugs. By automatically injecting subtle, realistic bugs—known as mutations—into your codebase and running tests in parallel, it calculates a 'Mutation Score' that reflects true test integrity. The skill identifies 'zombie tests' that pass even when the code is broken and provides actionable refactoring proposals to consolidate redundant tests and strengthen assertions, making it indispensable for maintaining high-quality code in critical paths like payments, security, and core business logic.

Key Features

01Parallel test execution using isolated git worktrees to prevent workspace pollution.

02AI-powered refactoring proposals to reduce test redundancy and improve execution speed.

03Smart context detection to automatically target recently modified files and related tests.

04Semantic mutation generation for boundary conditions, return values, and boolean logic.

051 GitHub stars

06Automated identification of 'zombie tests' that fail to catch introduced bugs.

Use Cases

01Auditing high-stakes code like payment processing or authentication logic before a major production release.

02Cleaning up bloated legacy test suites by identifying and removing redundant assertions that don't add value.

03Validating the effectiveness of new test cases during the development of complex features and edge cases.

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add citadelgrad/scott-cc mutation-test

For use in Claude.ai and ChatGPT

Download Skill