test-driven-development

To start test-driven development, design a failing unit test that defines the desired behavior before writing any production code. Implement only enough code to make that test pass, ensuring the feature is verified from the start.

The red-green-refactor workflow in unit testing moves from a failing test, to minimal passing code, to clean refactoring. This sequence ensures you validate behavior first, achieve correctness, and then improve code structure without losing test coverage.

To prevent regression risk when fixing software bugs, turn the bug into a reproducible failing test first. Implement the fix to make it pass, ensuring the specific behavior is verified and preventing future regressions from reoccurring.

Yes, test-driven development works for refactoring production code by validating behavior changes through test-first implementation. You enforce a failing test before modifying the code, ensuring the refactoring maintains correctness and reduces hidden regression risk.

Avoid over-mocking in unit tests because test-heavy mocks create false confidence and brittle implementations. Using real behavior in tests ensures they remain meaningful and accurately validate production code rather than just testing the mocks themselves.