What problem does it solve? A test suite that stays green against deliberately broken code proves nothing. This Skill verifies that googletest (make test:<name>) or Python/unittest suites actually detect breakage by applying 4-7 deliberate mutations to the code under test and confirming each one is caught by the intended test. ## Core Features & Use Cases - Mutation sweep for googletest and Python/unittest: Provides ready-to-adapt shell harnesses that apply a mutation, run the suite, record which test failed, and restore the source between mutations. - Fail-open trap detection: Documents the three silent failure modes (ANSI escape codes hiding gtest failure lines, mutations that never applied, and Qt aborting the interpreter before unittest prints a summary) that make a broken harness report every mutation as "still green". - Structured reporting: Produces a mutation-to-test mapping table suitable for a PR body, proving the tests are worth their line count. - Use Case: After writing a new *_test.py suite for a PyQt feature, run three mutations against the changed module and confirm each is caught by its intended test before opening the PR. ## Quick Start Mutation-test the test suite I just wrote by deliberately breaking the code under test several ways and confirming each mutation is caught by the intended test.
