Test-Driven Development (TDD)

When to Use

• New feature development
• Bug fixes (write test that reproduces bug first)
• Refactoring (ensure tests exist before changing)
• Any behavior change

When NOT to Use

• Prototyping or throwaway code with explicit user approval to skip tests
• Configuration-only changes (e.g., environment variables, CI config, linter rules)
• Documentation updates that do not affect runtime behavior

The Red-Green-Refactor Cycle