test-driven-development

Test-driven development prevents regressions by using a continuously verified test suite as a safety net. You refactor code to improve structure only after achieving a passing green state, ensuring existing behavior expectations remain intact throughout the process.

The red green refactor cycle is a test-first workflow where you write a failing test to confirm missing behavior, implement minimal code to make it pass, then improve code structure while keeping the tests green to guarantee correct software changes.

To start writing unit tests for a new feature, create a minimal failing test that demonstrates the specific missing behavior. Run it to confirm it fails for the expected reason, then write the smallest implementation change required to turn the test green.

Use a failing-first test workflow for bug fixes when you need to clarify and continuously verify behavior expectations. Writing a test that reproduces the bug ensures your implementation directly addresses the defect and prevents future regression.

No, during the minimal implementation step of TDD you should implement only enough code to make the failing test pass. Adding extra behavior violates the test-first workflow and introduces unverified changes into the software.