Which principle emphasizes writing tests before the actual code?

The principle that emphasizes writing tests before the actual code is Test-Driven Development (TDD). This development methodology promotes the idea of creating a test for a piece of functionality before writing the code that implements that functionality. TDD follows a cycle often referred to as Red-Green-Refactor.

In this cycle, the first step is to write a failing test (Red), which clearly defines the expected behavior or output of a feature. Once the test is created, the next step is to write the minimum amount of code necessary to make the test pass (Green). Finally, developers refactor the code to improve its structure and maintainability while ensuring that all tests still pass. This approach helps in ensuring high code quality, maintainability, and facilitating changes by providing a suite of tests that verify the correctness of the code at all times.

While Behavior-Driven Development (BDD), also involves tests focused on the behavior of the application from an end-user perspective, it does not strictly dictate the order of writing tests before code as TDD does. Code-First Development focuses on writing code without the emphasis on tests first, and Documentation-First Development is aimed at producing thorough documentation prior to code, neither of which aligns with the core tenet of T