To assess the quality of a product or service, you test it, right? But what if you could test it before it even exists? It seems impossible, but conceptually speaking, that’s exactly what the test-driven development approach advocates.

In today’s economic landscape, where technology companies play a central role, they set the trends—including how quality management is carried out for products and services. And the current paradigm in the software industry is that of continuous improvement.

To ensure that software is frequently updated, quality practices are implemented starting from the conceptual phase and, above all, extending through to the production environment. The systems are constantly monitored, and we maintain a continuous focus on quality, thereby adopting a " quality as a service" strategy.

In other words, the quality of applications necessarily depends on continuous and extensive validation at every stage of development. To ensure that every small piece of code is created in accordance with quality requirements, we use a test-driven development approach—one of the most widely adopted methods in the industry—to increase system reliability at every stage of production and reduce the amount of testing required during the release phase. Join us in this article to learn more about this practice!

Principles and Procedures

The test-driven development approach—known worldwide by the acronym TDD, which stands for Test-Driven Development —was developed by software engineer Kent Beck at the turn of the 21st century. According to Kent himself in his book, which gives the approach its name, TDD is a way of developing code geared toward the automated tests that the code will undergo. If the code block fails the test, new code is produced. It is an approach aimed at generating clean, functional code.

As defined by the approach itself, TDD requires unit tests and automated testing for code development and, consequently, for applications. In other words, testing is performed concurrently with development, detecting defects early on and creating a “safety net” starting with the smallest parts of the application. This prevents errors from escalating to larger modules within the system.

In a classic test-driven development workflow, the programmer follows five steps:

1. Write a test that will fail → Write a test for a feature that doesn't exist yet. Since there is no code to test, it will fail. This step serves only as the "requirements specification" for the code that is about to be written
2. Run the test → Run the test and watch it fail. First, to verify that the test itself was written correctly, and second, to check that it is actually testing what was intended to be inspected
3. Write as little code as possible → Write the first block of code, but only the minimum necessary to pass the test
4. Run the test again → Run the test again to see it pass this time. This confirms that both the inspection and the code were done correctly
5. Code refactoring → Once the code and tests are “ready,” the developer should review the code to improve its design, readability, and performance, if necessary. The key point to keep in mind is that refactoring should not break the tests that have already been written.

These five steps are summarized in the approach’s most fundamental principle: red/green/refactor. Steps one and two are the “red light”: the test will fail. Steps three and four are the “green”: code approved. Step five is refactoring, aimed at further improving code quality.

Test-driven development: how it helps create better applications

Based on the principles and procedures of TDD, one benefit of this approach is already evident when compared to others: documentation. When test-driven development is applied, not only does code review occur concurrently with development, but part of the quality assurance documentation is also generated, since tests and code blocks are written almost simultaneously.

Applications developed using TDD have significantly fewer defects than those created using other methodologies. This is because TDD ensures maximum granularity in unit tests and, to a large extent, rigor, since every small block of code is inspected.

The benefits of this approach are well documented in the technical and scientific literature. Case studies of projects at Microsoft and IBM have shown that the pre-release defect density in systems that used TDD fell by between 40% and 90% compared to similar projects that did not use the approach. On the other hand, code development time itself increased by between 15 and 35%.

First introduced approximately 25 years ago, the test-driven development approach has evolved into two other approaches that are also widely used in the industry: behavior-driven development and acceptance test-driven development. Both methods are conceptually grounded in TDD but are not exclusively test-driven.

Since its inception, Inmetrics has been a pioneer in strategies to improve the quality of critical systems. In our Digital Experience unit, we focus on safeguarding the end-customer experience and your company’s reputation by serving as your advisor and partner throughout your quality journey.

If you want the peace of mind that your applications aren’t damaging your reputation or hurting your business, click here to get in touch! Our experience working with large companies and our expertise in quality strategies are at your disposal—just speak with one of our specialists by clicking here!