What does "Test-Driven Development" (TDD) involve?

Test-Driven Development (TDD) is a software development approach that emphasizes the importance of writing tests prior to writing the actual code. This methodology involves a repetitive cycle of defining specific behaviors or requirements through tests, then writing the minimal amount of code necessary to pass those tests, followed by refactoring the code to improve its structure without altering its behavior.

By creating tests before the corresponding code, developers ensure that they have a clear understanding of the desired functionality. This practice leads to better-designed, more reliable software, as it encourages developers to think critically about how their code should behave from the outset. It also facilitates easier maintenance and debugging, as the tests provide a safety net that can catch regressions and other issues when code changes are made.

In contrast, the other options focus on approaches that do not align with the core principles of TDD. Writing tests after completing the application goes against the TDD practice, as it lacks the proactive approach to design and development that TDD advocates. Integrating tests into the deployment process might be part of a broader testing strategy, but it does not specifically encapsulate the essence of TDD. Lastly, focusing solely on UI testing neglects the broader range of testing that TDD encompasses, which includes unit tests,