Maintaining System Functionality and Clean Code
In Test-Driven Development (TDD), any changes made to the system should not break its existing functionality. The goal is to ensure the code continues working as before, even as modifications are made. Working code is essential, but it is crucial to maintain clean and well-designed code. One of the fundamental principles of this approach is to keep the system functioning.
The key is to keep interfaces tight and small, minimizing dependencies between components. A sizable system will have complex logic, but reworking the design adds value rather than cost. We should not consider our job complete once the program works; instead, we should focus on organization and cleanliness. Keeping software flexible involves leaving options open, especially those that support the application.
Duplication is detrimental to a well-designed system, so we should strive to drop it. After making the code expressive and descriptive, we must hunt for and remove duplicated code. We can improve visibility by moving extracted methods to separate classes. Quality must be improved when obscured domain logic makes bugs hard to find and implement. If agility is compromised, productivity decreases, and the benefits of TDD are lost.
Testing alone does not guarantee correctness; if tests fail, it is essential to investigate and address the failures. Programming is a craft, and making drastic structural changes to a program in the name of improvement can often lead to adverse outcomes. TDD helps mitigate this risk. We should follow some guidelines to write code that is easy to change. The reusability of existing code is valuable, and adding new code is preferable to extensive modifications. Code without side effects is more straightforward to change as it avoids cascading issues. Measuring the changes required in a codebase when faced with new needs can help check its structure.
