mutation-testing

Run and interpret Stryker mutation testing for JavaScript/TypeScript projects.

2|Updated Feb 23, 2026

Search Tags:#typescript #testing #javascript #test-coverage #mutation-testing #stryker

Ready to run

npx skills add https://github.com/jonmumm/skills --skill mutation-testing-jonmumm

💬 Prompt for ChatGPT / Claude Chat▼

Please help me install this Agent Skill.
Skill: mutation-testing
Source: https://github.com/jonmumm/skills/tree/main/mutation-testing
Command: npx skills add https://github.com/jonmumm/skills --skill mutation-testing-jonmumm

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

Mutation testing validates that your test suite actually detects behavioral changes by mutating code and ensuring survivors fail tests; this helps prevent false confidence when tests pass without catching real regressions.

Core Features & Use Cases

Stryker mutates source code to reveal gaps in test coverage.
Interpret survivors to drive targeted test improvements and achieve a high mutation score.
Use after implementing tests (TDD) to enforce quality gates and maintainable code.

Quick Start

Run an initial mutation test baseline and then execute incremental mutations to identify gaps in coverage.

Frequently Asked Questions about mutation-testing

High-intent search queries and answers about installing and using this skill.

FAQPage Schema

Why does mutation testing matter for validating test suites after TDD?▼

Mutation testing validates that your test suite detects behavioral changes by mutating code and ensuring survivors fail tests, preventing false confidence when tests pass without catching real regressions.

How do I run Stryker mutation testing to verify JavaScript test quality?▼

Run an initial mutation test baseline using the test:mutate npm script, then execute incremental mutations via test:mutate:incremental to identify gaps in coverage and achieve a high mutation score.

Do I need Vitest or Jest to use Stryker mutation testing?▼

Yes, you need a compatible test framework like Vitest or Jest. You also require a Stryker setup with a stryker.config.mjs file and specific npm scripts configured before running mutation tests.

What is the best way to interpret Stryker mutation survivors to improve coverage?▼

Interpret survivors to drive targeted test improvements. Analyzing surviving mutants reveals exactly which behavioral changes your current tests miss, allowing you to write specific assertions that achieve a 95% mutation score.

Can I use mutation testing for quality gates and test maintenance in TypeScript?▼

Yes, mutation testing applies to JavaScript and TypeScript projects using Stryker to enforce quality gates and maintainable code. It is used after implementing tests to validate test suites and ensure long-term test maintenance.