mutation-testing-js

Apply mutation testing to JavaScript and TypeScript test suites with Stryker.

23|2|Updated Jan 11, 2026

Search Tags:#typescript #javascript #code-review #mutation-testing #test-quality #stryker #branch-analysis

Ready to run

npx skills add https://github.com/eferro/augmentedcode-skills --skill mutation-testing-js

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

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

Mutation testing answers the question: "Are my tests actually catching bugs?" This skill helps you assess test effectiveness for JavaScript and TypeScript projects by introducing mutants and evaluating whether tests kill them.

Core Features & Use Cases

Systematic mutation analysis to identify weak tests on changed code.
Guidance on applying mutation operators (arithmetic, conditional, logical, etc.) to JS/TS.
Integration with Stryker for automated mutation testing and incremental branch analysis.
Practical workflow for evaluating mutants (Killed, Survived, No Coverage, etc.) and actionable improvements.

Quick Start

Install Stryker in your project and run mutation testing against your source files. For example: npx stryker run

Frequently Asked Questions about mutation-testing-js

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

FAQPage Schema

What is mutation testing and how does it reveal weak JavaScript tests?▼

Mutation testing reveals weak JavaScript tests by systematically introducing small code changes, called mutants, to evaluate if your test suite catches them. If a mutant survives, your tests have gaps in logic or coverage that need improvement.

How do I run mutation testing on my TypeScript project using Stryker?▼

You can run mutation testing on TypeScript projects by installing the Stryker toolkit and executing the command `npx stryker run` against your source files. This process applies operator mutations and branch analysis to evaluate test effectiveness.

Does mutation testing work with Node.js and exclude test files from analysis?▼

Yes, mutation testing requires Node.js and the Stryker toolkit to run against your source files. The analysis typically excludes test files to focus mutation operators on your actual JavaScript and TypeScript code changes.

How do I interpret mutation testing results like Killed, Survived, and No Coverage?▼

Mutation testing results like Killed, Survived, and No Coverage indicate whether your tests effectively caught bugs. Killed mutants mean tests passed, Survived indicates weak tests, and No Coverage shows missing test paths to guide actionable improvements.

What types of mutation operators are applied during JavaScript code analysis?▼

Mutation testing applies systematic mutation operators such as arithmetic, conditional, and logical mutations to JavaScript code. These operators introduce small changes to evaluate whether your test suite catches the altered logic across code changes.