Mutation Testing

Mutation testing mutates production code and checks whether tests fail — surviving mutants are test blind spots. TDD guarantees tests exist; mutation testing guarantees they actually catch bugs.

When to run

• After /skill:tdd, before /skill:code-review — validate the tests you just wrote.
• Standalone: "are my tests any good?"
• When an agent wrote tests and you want to check they're not shallow.

Pipeline

1. Detect language — inspect the target directory for language markers (below).
2. Load the language reference — read the matching references/<lang>.md for tool choice, install, and run commands.
3. Run mutation tool — apply mutations, run tests per mutation.
4. Parse survivors — collect mutations where tests did NOT fail.
5. Report blind spots — markdown report grouped by file, with original vs mutated code.

Detect language