test-driven-development

Test-driven development enforces a RED-GREEN-REFACTOR sequence, requiring a failing test before any production code. You write a test defining the desired behavior, confirm it fails correctly, implement minimal code to pass it, and then safely refactor.

Yes, test-first development applies to bug fixes, refactors, and new components across .NET, Node, Python, and Kotlin. For reported bugs, it requires writing a failing regression test before applying the actual code fix to prevent future regressions.

The RED-GREEN-REFACTOR cycle is a unit testing sequence where RED means creating a failing test for new behavior, GREEN is writing minimal implementation code to make it pass, and REFACTOR is improving the code structure while keeping tests green.

Regression testing for reported bugs requires writing a failing test that reproduces the specific defect before changing production code. Once the minimal fix is applied and the test passes, the regression coverage ensures the same bug cannot reoccur later.

Yes, test-first development requires correct failure validation. You must confirm the test fails for the exact expected reason before writing production code, ensuring accurate test coverage and preventing false positives during the minimal implementation phase.