tdd-playbook

Test-driven development follows the red-green-refactor cycle: write one failing test, implement minimal code to pass it, then refactor when green. This discipline prevents over-engineering and keeps your implementation focused on actual requirements.

Domain-first testing captures core business logic and invariants in unit tests, which are faster to write, run, and maintain than UI tests. This approach reduces overfitting to interface details and ensures your domain behavior is solid before testing UI integration.

Incremental design in TDD involves describing one domain rule at a time, writing a minimal failing test for it, implementing just enough code to pass, and refactoring. This workflow reduces risk, makes debugging easier, and provides clear checkpoints for progress.

Enforce one failing test at a time, require minimal implementation to pass each test, and refactor only when tests are green. This strict red-green-refactor discipline prevents shortcuts, keeps code reviews focused, and makes knowledge transfer clearer for new team members.

TDD applies to new development through red-green-refactor cycles. For refactoring, ensure tests are green before making changes, then refactor with confidence that tests catch regressions. The discipline remains the same: minimal changes per step, tests always green before proceeding.