What is the primary benefit of mutation testing?

Mutation testing goes beyond code coverage by proving that your tests can actually detect changes in logic, ensuring your test suite is effective at catching real bugs.

Does this skill work if I don't have a test suite yet?

No, mutation testing requires an existing, passing test suite to function, as its purpose is to evaluate the quality of those existing tests.

Which programming languages and frameworks are supported?

The skill currently supports JavaScript and TypeScript via Stryker, Java via PIT (Pitest), and Python via mutmut.

What is a good mutation score?

A mutation score of 90% or higher is considered excellent, while a score below 50% indicates that the test suite needs significant improvement to be reliable.

How does mutation testing affect build performance?

Mutation testing is compute-intensive because it runs your test suite multiple times. It is recommended to run it on specific modules or use incremental modes in CI pipelines.

Mutation Testing Analyzer

Name: Mutation Testing Analyzer
Author: cskiro

bycskiro

0•

Seguridad y Pruebas

Validates the effectiveness of test suites by introducing deliberate code mutations to identify surviving bugs and weak test cases.

The Mutation Testing skill empowers developers to look beyond traditional code coverage metrics by assessing the actual quality and resilience of their test suites. By automatically introducing subtle code changes—known as 'mutants'—into the codebase and verifying whether existing tests detect them, it provides a comprehensive mutation score that highlights logic gaps, missing validations, and boundary condition failures. This skill is indispensable for high-stakes projects where passing tests aren't enough, helping you ensure that your test suite is robust enough to catch real-world regressions across JavaScript, TypeScript, Java, and Python environments.

Características Principales

01Detailed analysis of surviving mutants to pinpoint specific testing gaps

02Automated identification of mutation targets and test execution workflows

03Multi-framework support for Stryker (JS/TS), PIT (Java), and mutmut (Python)

04Comprehensive mutation score reporting and data-driven interpretation

05Strategic recommendations for improving test effectiveness beyond line coverage

060 GitHub stars

Casos de Uso

01Setting up advanced quality gates in CI/CD pipelines to prevent weak tests from reaching production

02Auditing mission-critical modules for boundary condition and logic inversion resilience

03Verifying test suite effectiveness when code coverage is high but confidence remains low

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add cskiro/claudex mutation-testing

For use in Claude.ai and ChatGPT

Download Skill