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mbjmbjCommunity·1 Agent Skills Included

mutant

Mutation testing for Ruby that proves your tests actually work

Runs mutation testing on Ruby code by systematically modifying it and checking whether your tests catch each change. Exposes shallow, AI-generated, or incomplete tests that pass but verify nothing meaningful. Guides your agent to fix every surviving mutation by adding a missing test or simplifying the code, then re-runs until coverage reaches 100%.
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npx skills add mbj/mutant --all -g -y

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mutant

Run mutation testing for Ruby projects with RSpec or Minitest.

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Frequently Asked Questions

FAQPage Schema
How to install mutant?▼

Run `npx skills add mbj/mutant --all -g -y` in your terminal to install this skill globally for your AI agent.

What is mutation testing in Ruby?▼

Mutation testing automatically makes small changes to your code and checks if your tests fail as a result. If a change survives, your tests have a gap that mutant helps you close.

How do I fix an alive mutation?▼

Either add a test that fails against the mutated code, or accept the mutation as a code simplification. The skill walks your agent through both options until coverage hits 100%.

Does mutant work with RSpec, Minitest, and Rails?▼

Yes. Mutant supports RSpec, Minitest, and Test::Unit, and runs against Rails apps with parallel database isolation for PostgreSQL and SQLite.

Is mutant free to use?▼

It is free for open source projects with the --usage opensource flag. Commercial use requires a paid subscription per developer.

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