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From grimoire
Evaluates test suite adequacy by analyzing line/branch coverage and mutation testing scores to identify meaningful coverage gaps.
How this skill is triggered — by the user, by Claude, or both
Slash command
/grimoire:audit-test-coverageThe summary Claude sees in its skill listing — used to decide when to auto-load this skill
Evaluate test suite quality by analyzing both line/branch coverage metrics and mutation testing scores to identify meaningful gaps.
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Evaluate test suite quality by analyzing both line/branch coverage metrics and mutation testing scores to identify meaningful gaps.
Adopted by: Google (internal coverage standards), PIT mutation testing (Pitest — used across Java OSS ecosystem) Impact: Mutation testing (Pitest) studies show that 80% line coverage can correspond to as low as 40% mutation score — meaning half the bugs survive despite passing coverage thresholds. Google's internal research found diminishing returns above 85% line coverage for most code.
Why best: Line coverage is a floor, not a ceiling. It tells you which lines execute during tests, not whether tests would catch a bug. Mutation testing injects real bugs and checks whether tests detect them — a far stronger signal of test quality.
Coverage gap analysis:
PaymentService.refund() — 0% branch coverage, 4 survivors in mutation testelse paths.npx claudepluginhub jeffreytse/grimoire --plugin grimoireComputes code coverage for active track or module, targeting 95%+ coverage with report and justification for uncovered lines. Complements TDD workflow.
Analyzes test coverage reports (lcov, cobertura, istanbul) to identify gaps in lines/branches/functions, map to requirements, recommend tests, and track trends.
Performs mutation testing using Claude as the mutation engine: generates code mutants, runs tests, tracks kill/survive rates, identifies test gaps, and recommends test improvements. No external mutation tools required.