test-driven-development

To enforce test-driven development, you must require a failing test before any production code is written. This skill guides teams through a deterministic RED-GREEN-REFACTOR cycle, ensuring tests drive feature development and bug fixes to prevent undetected regressions.

The RED-GREEN-REFACTOR cycle is a test-first workflow where you write a failing test, implement just enough code to pass it, and then refactor. This repeatable process improves software maintainability, ensures requirements are validated, and builds confidence during upgrades.

You need a test framework like pytest and a project structure that supports tests. The workflow requires tooling to run tests and report failures, ensuring early feedback and establishing quality gates before you implement production code for features or bug fixes.

Apply test-first development by writing a failing test that validates the specific bug or new feature requirement. Once the test fails, implement the minimum production code required to pass it, run the tests again, and refactor to maintain software quality.

You should not use a test-first workflow if your project lacks a supporting test framework or project structure for running tests. Without tooling to report test failures and provide early feedback, the deterministic RED-GREEN-REFACTOR cycle cannot be effectively enforced.

The best way to prevent undetected regressions is enforcing a test-first workflow. By requiring a failing test before implementation and following the RED-GREEN-REFACTOR cycle, you ensure early feedback and validate requirements before production code is merged.