beck-test-driven-development

Test-driven development (TDD) is a coding discipline where you write a failing test first, implement the minimal code to make it pass, and then refactor safely. This red-green-refactor cycle drives design through fast feedback and small iterative steps.

Start using TDD for refactoring legacy code by writing tests that capture the existing behavior before making changes. Apply the red-green-refactor cycle in small baby steps to ensure the test suite remains safe and validates improvements throughout the refactoring process.

For unit testing in TDD, you should use the Arrange-Act-Assert or Given-When-Then patterns. These structures help organize your failing tests clearly, ensuring that the test setup, execution, and verification phases are distinct and maintainable throughout the refactoring process.

Yes, test-driven development applies directly to new feature development and small tasks. By practicing baby steps and the You Aren't Gonna Need It (YAGNI) principle, you write the simplest code to pass a failing test, ensuring focused and iterative progress.

You should avoid test-driven development when exploring throwaway prototypes or spiking unknown APIs where writing tests first creates unnecessary friction. TDD is most effective for feature development, refactoring legacy code, and establishing disciplined coding practices rather than initial exploratory coding.