test-driven-development

To start test-driven development, write a failing unit test for a new function before implementation, then write the production code to make it pass, and finally refactor. This enforces the red-green-refactor cycle.

The red-green-refactor cycle in TDD is a disciplined process: write a failing test, implement code to make it pass, and then refactor. It prevents shipping untested or poorly tested software.

Writing tests before implementation eliminates the risky practice of writing tests after coding, which often leads to missed bugs. It ensures robust, maintainable software by mandating a failing test first.

Test-driven development works for UI components and API endpoints by requiring adherence to specific testing patterns. It also covers pure functions and error handlers to ensure comprehensive code quality.

The best way to ensure code quality for an authentication module is using test-driven development: write tests for valid login, invalid password, and non-existent user scenarios before writing any authentication code.