test-driven-development

Test-driven development requires starting with a minimal failing test, confirming the explicit failure, and then writing only the code needed to pass. This test-first workflow reduces regressions and guesswork during software development.

The red-green-refactor cycle is a strict TDD sequencing method where you verify a failing test (red), implement minimal code to pass it (green), and then refactor safely. Explicitly verifying each stage ensures the test is meaningful and the code change is safe.

Use test-driven development for bug fixes and refactoring when confidence and repeatability matter. It prevents unverified production code by defining expected behavior through failing tests first, ensuring safe behavior changes and regression prevention in testable codebases.

Yes, pytest supports the test-driven development workflow. You use it to write a failing test for your next change, run it to verify the failure, implement the smallest code needed to pass, and rerun the full test suite for regression checking.

Limitations of test-first development include its strict requirement for testable codebases and the rigid red-green-refactor sequencing. It is less suited for codebases where behavior cannot be easily isolated or when rapid prototyping outpaces writing explicit failure verification tests.