TDD: Red → Green → Refactor

Test-Driven Development is a design loop, not a coverage ritual. A failing test names the next behavior. Production code exists only to make that test pass. Refactor only while green.

"The goal is clean code that works." — Kent Beck, Test-Driven Development by Example

Language-specific test APIs live in python-development, javascript-typescript, and golang-development. This skill owns the cycle, laws, and when to stop. Architecture tests (fitness functions) belong in evolutionary-architecture.

When to use