Mutation Testing
- 196 repo stars
- Updated July 25, 2026
- secondsky/claude-skills
Validate test-suite effectiveness with mutation testing using Stryker (JS/TS) and mutmut (Python) to find weak tests.
About
A testing skill that validates test effectiveness through mutation testing with Stryker for JS/TS and mutmut for Python. A developer uses it to find weak tests that pass despite injected code mutations and to raise overall test-suite quality before shipping.
- Mutation testing
- Stryker (JS/TS) + mutmut (Python)
- Finds weak tests
- Improves test quality
Mutation Testing by the numbers
- Data as of Jul 28, 2026 (Skillselion catalog sync)
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| repo stars | ★ 196 |
|---|---|
| Last updated | July 25, 2026 |
| Repository | secondsky/claude-skills ↗ |
What it does
Validate test-suite effectiveness with mutation testing using Stryker (JS/TS) and mutmut (Python) to find weak tests.
README.md
Mutation Testing Skill
Validate test effectiveness with Stryker (TypeScript) and mutmut (Python).
Overview
Expert guidance for mutation testing - finding weak tests by introducing deliberate code mutations and checking if tests catch them.
Core Concept
- Mutants: Small code changes introduced automatically
- Killed: Test fails with mutation (good)
- Survived: Test passes with mutation (weak test)
- Score: Percentage killed (aim for 80%+)
When to Use
- Validate test effectiveness
- Find weak assertions
- Improve test quality
- After achieving high code coverage
- Before major releases
Tools Supported
- Stryker (TypeScript/JavaScript)
- Vitest runner (
@stryker-mutator/vitest-runner) - Bun native runner (
@hughescr/stryker-bun-runner) — forbun testprojects
- Vitest runner (
- mutmut (Python)
Quick Start
# TypeScript (Stryker)
bunx stryker run
open reports/mutation/html/index.html
# Python (mutmut)
uv run mutmut run
uv run mutmut results
Auto-Trigger Keywords
- mutation testing
- test effectiveness
- weak tests
- stryker
- mutmut
- test validation
- code mutations
- stryker-bun-runner
- bun test mutation
Source
Adapted from laurigates/dotfiles
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