tdd

The red-green-refactor loop for test-first development works by writing one failing test to define a behavior, implementing the smallest code change to pass it, and then refactoring safely while the suite stays green. This incremental validation reduces regressions across the codebase.

The best way to write integration tests for a new checkout flow is to define user-facing behaviors first, write tests against public interfaces and observable outcomes, and implement minimal changes per test to validate each path through the system.

You should write tests against public interfaces and observable outcomes rather than internal details. Behavior-focused testing ensures your suite validates real system paths and remains stable during refactoring without coupling to private implementation logic.

To plan the next behavior when fixing bugs with test-first development, clarify the public interface, prioritize the most important observable behaviors, write one failing test for that specific path, and implement only the minimal change needed to make the suite pass.

You should refactor during test-first development only after your test suite returns green. This ensures your structural improvements and code cleanup are validated by existing behavior-focused tests without introducing new regressions into the system.

You do not need prior integration coverage to start test-first development, but you must design behavior-focused tests for public interfaces and validate changes incrementally. This approach works for both new features and fixing bugs in existing codebases.