test-driven-development

Test-driven development starts by writing a failing test that describes the desired behavior before any production code exists. Write the test, watch it fail to confirm it's testing the right thing, then implement minimal code to pass it. This ensures your code is testable and behavior is verified from the start.

Red-green-refactor is TDD's core workflow: write a failing test (red), implement minimal code to pass it (green), then improve the code without changing behavior (refactor). This cycle prevents over-engineering, keeps code focused, and maintains test coverage throughout development.

Start by writing a failing test that reproduces the bug's exact behavior. Watch it fail to confirm you've captured the issue, then implement the fix to make the test pass. This prevents regression and documents the bug's root cause in executable form.

Yes. TDD works for refactoring by ensuring tests already cover the code you're changing. Write tests for current behavior first if missing, then refactor with confidence that tests catch any introduced bugs. This makes refactoring safer and more maintainable.

Watching tests fail proves they're actually testing your code's behavior, not passing by accident. A test that never fails means it may not validate anything meaningful. This verification step prevents false confidence and ensures your test suite genuinely guards against regressions.

TDD writes tests first, ensuring code is designed to be testable and behavior is specified upfront. Writing tests after code often misses edge cases and may test implementation details rather than behavior. TDD's test-first approach produces cleaner, more maintainable code and better specifications.