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name: tdd description: Enforces Test-Driven Development (Red-Green-Refactor) for rigorous code quality.

Test-Driven Development (TDD)

Priority: P1 (OPERATIONAL)

The Cycle (Red-Green-Refactor)

1. RED (Write Failing Test): Write a minimal test and confirm it fails.
2. GREEN (Make It Pass): Write the simplest code to make the test pass.
3. REFACTOR (Clean Up): Improve code without changing behavior.

Core Patterns

• AAA (Arrange-Act-Assert): Structure every test case in three distinct phases.
• F.I.R.S.T.: Tests must be Fast, Independent, Repeatable, Self-Validating, and Thorough.

The Iron Laws

1. Never write production code unless you have a failing test (The Iron Law).
2. Never skip the "Red" phase (verifying logic by watching it fail).
3. Never leave the code in a broken state at the end of a session.

Verification Checklist

• New function/feature has a corresponding test case?
• Did you see the test fail first?
• Does the code handle edge cases defined in tests?
• Are mocks used only when strictly necessary? (See Anti-Patterns)