Explain Test-Driven Development (TDD).

Test-Driven development is used in the development of software. In TDD, developers plan the software characteristics that they want to create and then write test cases for each characteristic before implementing it. Through test-driven development, we can get insight into both the quality of the implementation (does it work) and the design quality (is it well structured).

In the first case, the test case will fail because the code is not yet implemented, and this is usually referred to as the red phase. After that, code is written to ensure that the test case passes and does not break any components or current test cases; that phase is called the green phase. The developer should then refactor the implementation of the code by maintaining and cleaning the codebase and optimizing the efficiency. Repeat this process every time a new test case is added.