test-driven-development

To enforce the red-green-refactor cycle, you must write a failing test before any production code, iteratively implement the feature until the test passes, and then refactor safely to maintain code quality.

Writing tests after production code leads to late defect discovery and brittle designs because tests are retrofitted to existing logic rather than guiding the implementation, reducing reliability and maintainability.

Test-first development is needed during bug fixes to ensure a failing test reproduces the defect before code changes, guiding the fix and verifying behavior changes without introducing regressions.

Yes, test-driven development aligns with existing project tooling and CI workflows by documenting the testing protocol and guiding when to run tests throughout the feature implementation process.

The best way to start test-first development is to write a failing test for the desired feature, then iteratively implement production code until the test passes, followed by safe refactoring.

Yes, test-driven development is useful during behavior changes and refactoring, guiding engineers through a repeatable loop with clear expectations and checks to safely modify existing code.