test-driven-development

Test-driven development enforces writing failing tests before production code, then implementing minimal code to pass tests, and refactoring while tests stay green. This Red-Green-Refactor cycle prevents test-after habits and ensures tests govern your implementation from the start.

Red-Green-Refactor is a three-phase cycle: write a failing test (Red), implement minimal code to pass it (Green), then improve code quality without breaking tests (Refactor). This discipline ensures tests precede production code and guards against skipping tests or writing inadequate ones.

TDD applies to new features, bug fixes, and refactors. For each task, write a failing test first, then implement or fix code to pass it, ensuring all tests stay green throughout. This maintains consistent test coverage across your entire codebase.

Enforce strict discipline: write failing tests before any production code, avoid rationalizing incomplete test coverage, and verify tests fail before implementation and pass after. This Skill provides guidance on recognizing and preventing test-after habits that undermine TDD benefits.

Minimal code is the smallest implementation that makes the failing test pass, nothing more. This prevents over-engineering, keeps code focused on requirements, and ensures refactoring stays purposeful during the Refactor phase.