mutation-testing

Inject faults into code and execute tests to identify surviving mutants.

Updated Feb 3, 2026

Search Tags:#code coverage #test-driven development #test quality #software testing #mutation testing #assertion strength

Ready to run

npx skills add https://github.com/dhruvinrsoni/agentskills-garden --skill mutation-testing-dhruvinrsoni

💬 Prompt for ChatGPT / Claude Chat▼

Please help me install this Agent Skill.
Skill: mutation-testing
Source: https://github.com/dhruvinrsoni/agentskills-garden/tree/main/skills/40-quality/mutation-testing
Command: npx skills add https://github.com/dhruvinrsoni/agentskills-garden --skill mutation-testing-dhruvinrsoni

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

This Skill addresses the critical issue of low confidence in automated test suites, even when code coverage is high, by identifying tests that pass due to weak assertions or accidental correctness.

Core Features & Use Cases

Test Quality Verification: Injects small faults (mutants) into your codebase to see if your existing tests fail.
Identify Test Gaps: Pinpoints areas where tests are insufficient or assertions are too weak.
Improve Test Robustness: Guides the creation of new tests to specifically address surviving mutants, leading to a more reliable test suite.
Use Case: After writing unit tests for a new feature, run mutation testing to ensure that your tests would indeed fail if a critical part of the logic (like a conditional statement or a return value) were accidentally changed.

Quick Start

Run mutation testing on the 'src/utils/math.js' file and report the mutation score.

Frequently Asked Questions about mutation-testing

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

FAQPage Schema

Why do my unit tests pass with high code coverage but still miss real bugs?▼

High code coverage often hides weak assertions or accidental correctness, meaning tests pass even when logic is broken. Mutation testing solves this by injecting faults into your code and checking if your tests actually fail, identifying gaps in test quality.

How do I check my assertion strength using mutation testing?▼

You can check assertion strength by running mutation testing, which injects small faults into your codebase. If a mutant survives because your tests did not fail, it pinpoints areas where your assertions are too weak and generates recommendations for new test cases.

Does mutation testing work with different programming languages?▼

Mutation testing supports various languages through tools like PIT, Stryker, and mutmut. You can inject faults into your codebase regardless of your stack to verify test robustness and identify surviving mutants.

How do I verify test suite quality after writing unit tests for a new feature?▼

To verify test suite quality, run mutation testing to inject faults into your new feature's logic. This verifies that your existing tests will indeed fail if critical parts like conditional statements or return values are accidentally changed.

What is the best way to improve test robustness and eliminate surviving mutants?▼

The best way to improve test robustness is to run mutation testing to identify surviving mutants. The process guides the creation of new test cases specifically designed to kill these mutants, leading to a more reliable test suite.