test-driven-development

Test-driven development requires writing a failing test first, then implementing minimal code to pass it. This ensures your tests actually verify intended behavior rather than just passing after implementation. Start by defining what your code should do, write the test, watch it fail, then code the solution.

Red-green-refactor is a three-step cycle: write a failing test (red), write minimal code to pass it (green), then clean up without breaking tests (refactor). This discipline ensures tests drive design and prevent over-engineering while maintaining code quality.

By writing tests before implementation, you force yourself to define the exact behavior needed, including edge cases like invalid inputs. When you write code to pass the test, bugs become visible immediately because the test fails first, proving the validation was missing.

Yes. For any bug, write a failing test that reproduces the issue first, then implement the fix. This proves the bug existed and ensures your fix works while preventing regression when the test runs in future builds.

Test-driven development applies to any language and framework. The core discipline—failing test first, minimal implementation, refactor—remains consistent whether you're working in Python, Java, JavaScript, or others.