What problem does it solve? Writing tests after implementation often produces brittle, implementation-coupled tests that break during refactors and fail to verify real behavior. This Skill enforces a disciplined test-first workflow so every test verifies observable behavior through public interfaces. ## Core Features & Use Cases - Red-Green Loop Discipline: Enforces writing a failing test before any implementation, one vertical slice at a time, with no speculative features. - Seam Identification: Helps you define and confirm public interface boundaries (seams) with the user before any test is written, focusing effort on critical paths. - Anti-Pattern Detection: Flags implementation-coupled, tautological, and horizontally-sliced tests, with reference guides on good test structure and mocking at system boundaries only. - Use Case: When adding a checkout feature, use this Skill to agree on the public seams first, then drive the implementation one failing test at a time, mocking only external boundaries like payment APIs. ## Quick Start Ask the AI to build a new feature using test-driven development with the red-green-refactor loop, starting by agreeing on the seams to test.
