What problem does it solve? Writing tests after code often produces brittle, implementation-coupled tests that break on refactors and miss real behavior. This Skill enforces a disciplined red-green loop so tests verify behavior through public interfaces and survive refactoring. ## Core Features & Use Cases - Red-Green Loop Rules: Write the failing test first, then only enough code to pass it, one vertical slice at a time. - Seam-Based Test Design: Agree on public interface seams with the user before writing any test, keeping tests at boundaries rather than internals. - Anti-Pattern Detection: Identifies implementation-coupled, tautological, and horizontally sliced tests, plus mocking guidelines for system boundaries only. - Use Case: When fixing a bug, reproduce the defect as a failing regression test first, then apply the minimal fix so the regression test lands in the project's declared suite. ## Quick Start Ask the agent to build a new feature test-first using the tdd skill, starting by agreeing on the public seams to test.
