In this article, I will explain what test-driven development is, what the benefits of TDD are, and why you should use it in software development (especially when working with Agile).
What Is Test-Driven Development?
Test-driven development (TDD) is a software development process that relies on the repetition of a very short development cycle. First, the developer writes an (initially failing) automated test case that defines a desired improvement or new function, then produces the minimum amount of code to pass that test, and finally refactors the new code to acceptable standards. In test-driven development, automated unit tests are written before the code is actually written. Running these tests give you fast confirmation of whether your code behaves as it should or not.
Some people think that automated testing increases the amount of development time. However, we have been using TDD for many years and we can say with no doubt that automated tests actually allow developers and the team to develop the project much more quickly and with a higher quality.
Maybe knowing the advantages of TDD will convince you. Working with TDD for more than 10 years, we came to the conclusion that those are the 20 main benefits of test-driven development.
20 Benefits of Test-Driven Development
- Writing the tests first requires you to really consider what do you want from the code.
- You receive fast feedback.
- TDD creates a detailed specification.
- TDD reduces time spent on rework.
- You spend less time in the debugger.
- You are able to identify the errors and problems quickly.
- TDD tells you whether your last change (or refactoring) broke previously working code.
- TDD allows the design to evolve and adapt to your changing understanding of the problem.
- TDD forces the radical simplification of the code. You will only write code in response to the requirements of the tests.
- You're forced to write small classes focused on one thing.
- TDD creates SOLID code.
- TDD supports a clean interface.
- TDD creates code that is maintainable, flexible, and easily extensible.
- The resulting unit tests are simple and act as documentation for the code. Since TDD use cases are written as tests, other programmers can view the tests as usage examples of how the code is intended to work.
- The development time to market is shorter.
- The programmer’s productivity is increased.
- Development costs are cut.
- Quality is improved.
- Bugs are reduced.
- TDD gives programmers the confidence to change the larger architecture of an application when adding new functionalities. Without the flexibility of TDD, developers frequently add new functionality by virtually bolting it to the existing application without true integration, which can cause problems down the road.
When programming, the bigger the codebase gets, the harder it gets to move further or to change the code because it's easier to mess up. If you have automated tests, they become your safety net, allowing you to see what the mistake, where it is, and how it affects the system. It helps identify errors in a really short period of time. These tests give developers very fast feedback when something breaks. These tests are also called change detectors. When you make a change, the tests will detect very soon if there are any problems or mistakes.
TDD provides its best results when the code is constantly improved. The benefits of test-driven development have to do with more than just the simple validation of correctness. TDD can also drive the design of a program. Because of the testing modules that are built into the Continuous Integration development model, organizations using a TDD approach can easily make changes to their applications without the fear of breaking the application and hamstringing their daily operations.
TDD leads to more modularized, flexible, and extensible code due to the fact that the methodology requires that the developers think of the software in terms of small units that can be written and tested independently and integrated together later. This leads to smaller, more focused classes, looser coupling, and cleaner interfaces.
One of the benefits of test-driven development is that it gives organizations the ability to painlessly update their software to address new business requirements or other unforeseen variables. A successful organization is one that can react to changing environments and address improvement suggestions with aplomb. Test-driven development is the methodology that makes such flexibility, maintainability, and extensibility possible.