Run mutation testing for Ruby projects with RSpec or Minitest.
npx skills add https://github.com/mbj/mutant --skill mutant
Please help me install this Agent Skill. Skill: mutant Source: https://github.com/mbj/mutant/tree/main Command: npx skills add https://github.com/mbj/mutant --skill mutant
## What problem does it solve? Mutant provides a structured approach to mutation testing for Ruby projects, surfacing untested behaviors and helping teams verify coverage.
## Core Features & Use Cases
### Quick Start Bundle install and run mutant against your Ruby project to start mutation testing.
High-intent search queries and answers about installing and using this skill.
Mutation testing for Ruby introduces small code changes (mutations) and runs your test suite to verify each is caught. It surfaces alive mutations—untested behaviors—so you can add tests or simplify code.
Run mutation tests against your Ruby project using RSpec or Minitest by executing the mutant CLI after bundle install. It generates per-subject mutation coverage and alive mutation counts to guide test improvements.
Alive mutations are code changes that survive because your test suite fails to detect them. Fix alive mutations by adding tests to cover the untested behavior or by simplifying the code to remove unnecessary branches.
Yes, mutation testing integrates directly with existing RSpec or Minitest workflows. It runs within your current Ruby testing setup to evaluate test quality and verify coverage without changing your test framework.
Mutation testing goes beyond line coverage by actively verifying that tests detect code changes. It exposes alive mutations that traditional coverage metrics miss, helping you decide whether to add tests or simplify code.
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