test-driven-development

Test-driven development is a practice requiring a failing test before any production code. The red-green-refactor cycle forces you to write a failing test, implement minimal code to pass it, and then iterate safely.

Use unit testing to define and validate expected behavior before writing production code. By enforcing tests first during feature work, you catch regressions early and improve software reliability and maintainability.

You need test-driven development for refactoring when you want safer structural changes without altering behavior. Writing tests first validates existing behavior, ensuring your refactors do not introduce undetected regressions.

Yes, test-driven development applies directly to bug fixes and behavioral changes across software projects. You write a failing test that reproduces the bug, then implement the minimal production code to pass it.

The best way to start is to write a failing test first, then implement the absolute minimal production code required to make that test pass, and iterate through red-green-refactor cycles to refine the design.

Writing code without early tests leads to brittle implementations because behavior is not validated before coding. Test-driven development solves this by forcing tests to define expected behavior prior to writing production code.