Now that we have our tests written, how can they be integrated into the development process? Currently, we are using our tests in order to ensure code correctness after we create a feature. But, what if we flipped the order and used tests in order to create correct code from the beginning? This is what test-driven development (TDD) advocates.

TDD follows a simple loop to write the code of a new feature in your application:

In a project that uses TDD, the first thing that you write, before any of the code that controls what you are actually building, is the tests. What this forces the programmers on the project to do is to plan out the project's scope, design, and requirements before writing any code. While designing APIs, it also forces the programmer to design the interface (or contract) of the API from a consumer's perspective, rather than...