test-driven-development

To write a failing test before implementing new code, define the desired behavior with a test that fails initially, then implement the smallest code change required to pass it. This enforces a strict test-first workflow for reliable software changes.

The red-green-refactor workflow is a test-driven development cycle where you write a failing test, implement the minimal code to make it pass, and then safely clean up the code. It ensures verified behavior and regression coverage.

To reproduce a bug fix with a test, write a test that exposes the defect and fails against the current codebase before making any changes. This ensures the regression stays covered once the minimal code fix is applied.

Common testing anti-patterns to avoid with mocks include testing the mocks instead of real behavior, or adding test-only methods to production code. Testing guardrails prevent these mistakes by enforcing real-behavior verification.

Test-driven development works for safe refactoring by ensuring existing behavior is covered by verification tests before you clean up the code. This prevents unverified code changes and maintains regression coverage during structural improvements.