What problem does it solve?
This Skill solves the risk of shipping unverified changes by enforcing a test-first workflow that proves the feature works before any production code is added.
Core Features & Use Cases
- Red-Green-Refactor TDD loop: write a failing test, verify it fails for the expected reason, implement minimal code to pass, verify all tests pass, then refactor without changing behavior.
- Iron Law for quality: requires a failing test first and rejects rationalizations like “just this once,” “test later,” or “keep it as reference/adapt existing code.”
- Anti-pattern guardrails for testing: discourages testing mock behavior, adding test-only methods to production code, mocking without understanding dependencies, and incomplete mocks.
Use it when implementing any new feature, fixing a bug, or refactoring while needing strong confidence and regression protection (especially when your agent or team tends to code before validating behavior).
Quick Start
Use the test-driven-development skill to guide the agent to implement changes by writing a failing test, verifying the failure is for the missing feature, writing the smallest production code to make it pass, then running the test suite to confirm no regressions.
