test-driven-development

Test-driven development enforces writing a failing unit test before writing production code to prevent software regressions. You then implement minimal code to pass the test, and refactor while keeping tests green.

To apply TDD during refactoring, maintain a safety net of green tests that guard against unintended behavior changes. Write targeted tests for existing behavior, verify they pass, then refactor incrementally while keeping tests green.

Yes, this test-driven development cycle is applicable to both new feature development and bug fixes across software projects. It guides developers through a repeatable cycle of writing failing tests before implementing minimal code to fix or build features.

Writing unit tests before production code enforces failing tests initially, ensuring your test validates the feature. Writing tests after coding risks tests that simply mirror existing logic, missing the regression protection and minimal implementation discipline of TDD.

You should avoid the Red-Green-Refactor workflow for exploratory prototyping or throwaway scripts where regression protection is unnecessary. TDD requires writing failing tests first, which adds overhead unsuitable for rapid, unstable software experiments.