test-driven-development

Test-driven development (TDD) is a test-first workflow where you write a failing test (red), implement minimal code to pass it (green), and then refactor while maintaining correctness. This enforces software quality through rapid feedback and regression-free changes.

To start writing unit tests before implementation, write a failing test that defines the desired behavior, then implement only enough code to pass that test. Repeat this red-green-refactor cycle for each new feature or bugfix to ensure software behaves as designed.

Yes, test-first development applies to bug fixes and refactoring. You start by writing a failing test that captures the bug or desired behavior, then implement the fix or refactor the code while ensuring tests maintain correctness and pass without regression.

Writing tests before code improves software engineering quality by ensuring behavior matches requirements and catching regressions early. This test-first discipline provides rapid feedback, safer changes across the codebase, and clearer design through strict red-green-refactor cycles.

The best way to ensure refactoring does not break existing unit tests is following the red-green-refactor cycle. After achieving a passing test, refactor the code while continuously verifying that the tests still pass, maintaining correctness and enabling regression-free changes across the codebase.

You should reconsider a strict test-first workflow when exploring unfamiliar prototypes where requirements are undefined. TDD enforces discipline for features, bug fixes, and refactors, requiring strict steps that may slow down rapid experimental coding where behavior is not yet designed.