test-driven-development

Test-driven development is a methodology where you write failing tests before implementation to verify behavior early. It improves code quality and reduces debugging time by ensuring robust test suites and living documentation throughout the development process.

Start writing tests before implementation by creating tests that define expected behavior for the new feature. Follow the red-green-refactor cycle: create a failing test, implement code to verify and pass it, then refactor while maintaining behavior verification.

Test-driven development works for bug prevention in existing software by emphasizing the creation of failing tests that reproduce the bug before applying a fix. This behavior verification approach ensures the fix is correct and prevents regression in the test suite.

The red-green-refactor cycle is a structured test-driven development approach with clear steps: create a failing test, write implementation code to pass it, then refactor the code. This cycle ensures behavior verification and maintains robust test suites throughout development.

You should avoid test-driven development when tasks lack clear behavioral expectations or require exploratory prototyping. Since this methodology prioritizes behavior verification and test creation before implementation, ambiguous requirements make writing robust test suites difficult and counterproductive.