test-driven-development

Test-driven development is a software development technique where you write failing unit tests before production code to verify intended behavior. It enforces a disciplined red-green-refactor cycle, ensuring every change is validated against explicit expectations and preventing regressions.

Yes, the red-green-refactor cycle is universally applicable for refactoring existing code, bug fixes, and behavior changes. You write a failing test to capture the desired new behavior, implement minimal code to pass it, and then safely refactor while maintaining continuous test validation.

The best way to make unit tests serve as living documentation is to write them first with comprehensive assertions before the production code exists. This test-driven approach guarantees tests are meaningful, explicitly define expected behavior, and remain accurate for future maintenance.

Yes, you need to write a failing test before fixing a bug to explicitly define the incorrect behavior and ensure your fix resolves it. This test-driven approach validates the bug fix against strict expectations and prevents future regressions by maintaining continuous test coverage.

Writing tests first improves code quality by requiring minimal production code to pass comprehensive assertions, which prevents over-engineering. This disciplined approach ensures every behavior change is validated upfront, eliminating untested code paths and reducing bugs.