test-driven-development

Test-driven development is a software testing process requiring a failing test before writing production code. The Red-Green-Refactor cycle involves writing a failing test, implementing minimal code to pass it, then refactoring for readability while keeping tests green.

To write tests before implementing new software features or bug fixes, first author a failing test that captures the intended behavior. Then implement the minimal production code required to make that test pass, ensuring correct behavior and preventing regressions.

Yes, you can use test-driven development for refactoring existing code. It mandates writing tests to validate current behavior before changes, allowing you to safely refactor for readability and maintainability while ensuring all tests stay green.

Test-driven development requires a failing test before writing production code to enforce the Iron Law of correct software behavior. This deterministic cycle ensures every code change is validated, preventing regressions and guiding structural test quality.

The best way to structure tests and name expectations in test-driven development is to capture intended behavior clearly within the initial failing test. This enforces test quality and maintainability throughout the subsequent refactoring step.