What problem does it solve? After implementation, test suites often miss edge cases, lack end-to-end coverage for boundary-crossing changes, and let mutation testing survivors slip through. This Skill hardens the test suite over a git-defined scope without ever touching production code. ## Core Features & Use Cases - Three-phase hardening: Fills unit test gaps for public functions, adds e2e tests for changes crossing system boundaries (HTTP routes, DB writes, external IO), and drives mutation test efficacy to at least 80% by killing LIVED mutants. - Strict read-only boundary on production code: Only test files, fixtures, mocks, and test configuration are writable; suspected production defects are recorded as findings with sequential TEST-NNN ids instead of being fixed. - Git-defined scope resolution: Works against a diff versus main, uncommitted changes, a single file, or the whole codebase, with fresh-eyes analysis independent of the implementer's narrative. - Use Case: After finishing a feature branch, run the Skill to add missing unit and e2e tests for the diff, run Stryker or gremlins on the changed paths, and receive a structured report listing any suspected defects the new tests exposed. ## Quick Start Use the test-dev skill to strengthen tests for the diff between my current branch and main, filling unit and e2e gaps and reducing mutation survivors.
