What problem does it solve? Developers and AI agents under pressure routinely write implementation code before tests, then rationalize that ordering does not matter, producing unverified code and tests that prove nothing. This Skill enforces a strict test-first discipline so every behavior is proven by a failing test before any production code exists. ## Core Features & Use Cases - Iron Law Enforcement: No production code without a failing test first; code written before the test must be deleted, not adapted or kept as reference. - Red-Green-Refactor Cycle: One minimal failing test per behavior, the simplest passing implementation, then refactoring only with green tests as a safety net, never batching acceptance criteria. - Rationalization Countermeasures: A table of common excuses ("too simple to test", "I'll test after") with rebuttals, plus red flags that force a restart and a verification checklist before claiming completion. - Testing Anti-Patterns Reference: Guidance against testing mock behavior, adding test-only methods to production classes, mocking without understanding dependencies, and incomplete mocks. - Use Case: When fixing a bug, write a failing test that reproduces it first, then implement the minimal fix and confirm the full suite stays green before marking the work complete. ## Quick Start Ask the agent to implement the next feature using strict test-driven development, writing and running a failing test before any production code.
