What problem does it solve? Code coverage tells you which lines ran during tests, but not whether tests would fail if the code were wrong. This Skill performs static pseudo-mutation analysis — reasoning about hypothetical code changes like boundary flips, boolean inversions, and removed null checks — to reveal test blind spots where bugs would slip through undetected. ## Core Features & Use Cases - Mutation Point Catalog: Identifies boundary, boolean, return value, exception, arithmetic, and null-check mutation points across 12+ languages including .NET, Python, TypeScript, Java, Go, Rust, and more. - Kill/Survive Classification: Classifies each mutation as Killed, Survived, No coverage, or Equivalent, with concrete recommended test fixes for every gap. - Risk-Prioritized Reporting: Produces a mutation score summary plus prioritized findings, ranking business-logic gaps above trivial code. - Use Case: Before merging a payment calculation change, ask whether your tests would catch a sign flip or off-by-one error — the Skill traces which tests exercise each line and whether their assertions would actually fail. ## Quick Start Ask the AI to analyze whether the tests for a specific module would catch subtle bugs like boundary changes or removed null checks in the production code.
