Mutation Testing

What it does

This skill enables AI agents to perform mutation testing, a method that validates code quality by introducing small faults into source files and verifying if existing tests detect them. It helps ensure test suites are robust enough to catch real bugs rather than just passing trivially.

When to use it

• You need to verify that your unit tests actually cover critical logic paths and aren't too permissive.
• You want to identify weak or redundant tests that fail to catch introduced errors.
• You are preparing a codebase for high-reliability deployment where test effectiveness is paramount.
• You aim to automate the detection of "brittle" test suites before they cause production issues.

Key capabilities

• Automatically injects mutations (faults) into your source code.
• Executes existing test suites against the mutated code.
• Reports which tests successfully detect the introduced faults.
• Highlights tests that fail to catch mutations, indicating gaps in coverage.

Example prompts

• "Run a mutation testing analysis on my src/utils directory and summarize the results."
• "Identify specific unit tests that are failing to detect mutations in the authentication module."
• "Generate a report showing the mutation score for my current test suite."

Tips & gotchas

Mutation testing can be computationally expensive, so it may take longer to run than standard unit tests. Ensure you have sufficient compute resources available before initiating large-scale analysis.