develop-tdd

TDD — Test-Driven Development

When this skill is loaded, the developer follows the Red-Green-Refactor cycle. The orchestrator loads this skill when the user requests TDD.

Cycle

1. Red — Write failing tests first. Tests define expected behavior from the task plan. Run them — verify they fail for the right reasons (not syntax/import errors).
2. Green — Write the minimum code to make all tests pass. No more.
3. Refactor — Clean up code and tests. No behavior changes. All tests still pass.

Rules

• Write tests before any implementation code
• Each test covers one behavior — name it after what it verifies
• Start with the simplest case, add complexity incrementally
• Run tests after every step (red, green, refactor) — report results each time
• Tests must fail for the right reason — a missing function, not a syntax error
• Do NOT write implementation and tests simultaneously
• Do NOT write all tests upfront — write one test (or a small batch), make it pass, then write the next

Test Quality

• Test behavior, not implementation details
• Include edge cases: empty inputs, nulls, boundary values, error conditions
• Keep tests independent — no shared mutable state
• Mock external dependencies, not internal logic
• Arrange-Act-Assert structure

Status Updates

After each TDD step, tell the orchestrator what happened in plain English, ≤50 words. Example: "Red: wrote 3 tests for auth middleware — all fail as expected. Files: src/auth.test.ts"