test-driven-development

Test-first development is enforced by applying the strict Red-Green-Refactor cycle, ensuring every production code change is justified by a failing test to prevent regressions and maintain high code quality.

The Red-Green-Refactor methodology is a test-first development cycle where you write a failing test, write the minimum code to pass it, and then refactor. It ensures implementation is driven by expected behavior.

A test runner like pytest is required to validate behavior before and after code changes. It provides the necessary automated testing framework to execute tests and verify that your features and bug fixes work correctly.

To implement a new feature using test-driven development, start by writing a failing test case that defines the expected behavior. Then write the implementation code to pass the test, followed by refactoring for clean code.

TDD applies to all software engineering tasks including bug fixes and refactoring. It maintains a comprehensive test suite that catches bugs immediately upon code changes, ensuring your refactoring does not introduce new regressions.

Writing failing tests before implementation code ensures every line of production code is justified by a test. This lack of confidence in code quality is resolved by a strict, systematic test-first development cycle.