test-driven-development

Test-driven development begins by writing a failing unit test that defines desired behavior, implementing minimal production code to pass it, and refactoring safely while maintaining a green test suite.

The red-green-refactor cycle is a test-driven development loop where you write a failing test, write just enough code to make it pass, and then refactor the implementation for clarity without breaking behavior.

Yes, test-driven development applies to bug fixes and refactoring by first writing a test that reproduces the bug or validates existing behavior, ensuring all changes are guarded by automated regression checks.

Test-driven development spans multiple programming languages and requires a minimal test suite discipline with a repeatable process to run tests, ensuring language-agnostic validation of feature additions and refactors.

Writing failing tests before production code clarifies requirements, reduces defects, and guides incremental design by providing clear failure feedback that validates expected behavior throughout the lifecycle.

Test-driven development may not suit exploratory spikes or throwaway prototypes where immediate behavior validation is unnecessary, as it requires maintaining a repeatable test process and minimal test suite discipline.