tddlisted

# TDD Skill ## What You Get - Failing test (RED) -> minimal implementation (GREEN) -> refactored code, committed at each green step - Full test suite passing with no mocks of internal modules ## Philosophy Tests verify **behavior through public interfaces**, not implementation details. Never test private methods directly. Never mock your own modules. Use **vertical slices**, not horizontal slices. Write one test, make it pass, repeat. Do not write all tests first then implement -- that is waterfall disguised as TDD. ## Workflow: 4 Phases ### Phase 1: Planning Before writing any code, confirm: - What is the public interface (function signatures, module API)? - What behaviors does the caller expect? - What are the edge cases and error conditions? Do NOT write code yet. Agree on the interface first. ### Phase 2: Tracer Bullet Write exactly ONE test for the simplest happy-path behavior. Run it. Watch it fail (RED). Implement the minimum code to make it pass (GREEN). This proves the test infrastructure works end-to-end. ### Phase 3: Incremental Loop For each remaining behavior: 1. Write ONE failing test (RED) 2. Implement minimum code to pass (GREEN) 3. If the code is messy, refactor NOW while green 4. Run the full suite -- all tests must pass 5. Repeat Never skip ahead. Never write two tests before making the first green. ### Phase 4: Refactor Only refactor when GREEN. Look for: duplication, shallow modules, long methods, feature envy, primitive obsession. Run the