Use mutation testing to measure how well tests detect bugs
SkillDev toolsThis is a mutation testing skill for AI agents. When applied, it lets the agent evaluate test quality on modules containing business logic, calculation utilities, or state machines, checking whether the tests provide genuine defect detection rather than just passing coverage.
Available today. Use it from your connected AI after setup.
No other account needed.
Have an AI agent that can load skills.
Then ask your AI: use the Use mutation testing to measure how well tests detect bugs skill
What your AI can do with it
- Evaluate test quality on modules containing business logic
- Assess whether tests on calculation utilities catch real defects
- Check test effectiveness on state machines
- Determine whether unit tests provide genuine defect detection
Getting started
- Have an AI agent that can load skills.
- Add the mutation-testing skill to the agent's available skills.
- Point the agent at the module with business logic, calculation utilities, or state machines whose tests you want evaluated.
- Ask the agent to apply the skill to determine whether the tests genuinely detect defects.
What this skill tells your AI
The instructions your AI receives, as published by thedaviddias/front-end-checklist in skills/mutation-testing/SKILL.md and read by ahel’s review.
A codebase can have 90% line coverage and still ship critical bugs if tests only execute code without asserting meaningful outcomes. Mutation testing reveals these gaps by proving that your tests can distinguish correct code from subtly broken code — the standard that actually matters in production.
Quick Reference
- Code coverage tells you which lines were executed; mutation score tells you which bugs were caught
- Stryker injects small code changes (mutations) and checks whether tests fail — if they don't, the tests are weak
- Aim for 80%+ mutation score on critical business logic paths
- Run Stryker on a focused scope (one module) rather than the whole codebase to keep CI times manageable
Check
Assess whether this module has mutation testing configured and whether the mutation score on critical paths meets the project's quality threshold.
Fix
Set up Stryker for this module, run an initial mutation report, and improve tests to kill surviving mutants in the critical business logic paths.
Explain
Explain what mutation testing is, how Stryker works, and why mutation score is a more meaningful quality signal than code coverage alone.
Code Review
Review the Stryker configuration and mutation report to identify surviving mutants in critical code paths, and suggest test improvements to kill them.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/en/rules/testing/mutation-testing
Signals
- GitHub stars
- 74k
- Forks
- 7k
- Last commit
- Aug 2026
ahel review
K1binfo
installs-packages (in references/rule.md)
Automated review, not a security audit. Ruleset v1+k2.
Questions
- What does this skill do?
- It lets an agent evaluate test quality on modules containing business logic, calculation utilities, or state machines, to determine whether the tests provide genuine defect detection.
- When should the agent use it?
- Use it when evaluating test quality on modules containing business logic, calculation utilities, or state machines.
- Does it run the tests itself?
- The skill is used to evaluate test quality; the item does not specify how execution is handled.
Advanced
- Item type
- skill
- Key
mutation-testing-thedaviddias- Source
- github.com/thedaviddias/front-end-checklist