The difference between behavior-driven design and test-driven design

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Teams have a number of strategies to choose from when it comes to evaluating their applications and ensuring that they stand up to user expectations. In many cases, agile software testing can quickly become confusing for quality assurance professionals due to the number of abbreviations and different types of testing approaches. In particular, behavior-driven and test-driven design have both become more popular, but many organizations don't understand the difference between these concepts or where they intersect. Let's take a look at what BDD and TDD are as well as how teams can use them to their advantage.

Dissecting design differences

To dig deeper into the unique characteristics of each approach, it's critical to understand what each one actually does. TDD mainly uses automated unit tests to give developers direction on how to design the software. This approach follows a set process: First, create a test that will make the code fail. According to ISTQB Exam Certification, this helps to ensure that the test is calling the correct code, and not working by accident. Then, teams will improve that code to make the test pass. The final stage of this method involves refactoring and removing duplication. It's expected that teams will repeat this cycle throughout the project's lifecycle, making it a perfect complement to agile and automation testing efforts.

BDD has drawn numerous similarities to TDD, often causing confusion among QA professionals. Amazon engineer Josh Davis noted that the big difference is the fact that BDD helps mitigate issues caused by TDD and is driven by behavior and specification. Rather than coding in a bunch of functions, BDD uses a style that is more akin to naturally writing sentences, essentially telling the code exactly what you want it to do. This is a major difference, as BDD directly impacts the actual design of the software, while TDD is more focused on the testing.

"The software tends to be better designed [with BDD], that is, loosely coupled and easily maintainable, because the developer is free to make design decisions and refactor at any time with confidence that the software is still working," ISTQB stated.

Which is better?

Now that the differences have been cleared up between these approaches, QA teams will likely want to know which one they should use. It is possible to use each method by itself, and the choice between them will largely depend on what teams want to focus more on and what experience they have with unit tests. Davis suggested getting the hang of TDD first, as many of its practices are used in BDD. If you're already using TDD but aren't getting the results that you expect, try out BDD.

Although each strategy can act on its own, teams may see more benefit from using them together. As in most cases, uniting approaches can help QA make the most of their skills and improve overall product quality.

"Unit Testing gives you the what. Test-Driven Development gives you the when. Behavior Driven-Development gives you the how," Code Utopia stated. "Although you can use each individually, you should combine them for best results as they complement each other very nicely."

Using BDD and TDD gives teams a significant advantage in app creation, but they will need the resources to handle all of the tests that they are generating. Test management tools help assign, edit and prioritize test cases for each project. Teams can also be kept on the same page with real-time updates and status changes to monitor overall progress. This type of solution will be a critical asset no matter what method teams choose to follow.

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