Software testing

How do TDD and BDD allow us to build quality software solutions?

How to build quality software solutions using TDD and BDD?

 When software engineers get involved in the project, their main goal is to deliver a quality product. Quality means 100% compliance with the requirements, lack of bugs and errors, high security, and the capability to handle high loads.

 The app or website should also add value to customers, work as intended, and provide an intuitive interface so that it can be used even without thinking. Although this all seems to be quite difficult, the best software development practices emerged to simplify and improve the creation of mobile and web solutions.

 In this article, we’ll tell you how test-driven development (TDD) and behavior-driven development (BDD)helps us write great code and create products that meet user expectations. Let’s begin!

Testing meme

What is test-driven development?

 TDD is a software engineering practice that implies converting a project specification into test cases, running them, preparing code scripts, and making tests pass. Tests are created before code development and are repeated until the app is ready. 

 Since the team focuses on the requirements first and only then on programming, they build what is actually needed faster and easier. As a consequence, you get quality software that fully meets the goals.

 You should also know that the TDD process isn’t about testing. As we’ve already mentioned, test cases are written by software engineers, not testers. The term “test” is used in the definition as test framework tools like Cucumber and Behat are used here but in a slightly different way.

Overview of the TDD process looks as follows:

1. Add a test

Each new product feature starts with preparing a test for a specific function or enhancements to it. The team develops test cases according to the technical specification in order to make the end solution work as needed. That’s why it’s so important for the team to clearly understand the project requirements that can be covered with use cases and user stories. 

2. Run tests 

A software engineer runs tests against what is currently implemented and observes them failing (as they are intended to since the functionality hasn’t been developed yet). This step allows programmers to see if all of them work and avoid errors in the new test.

3. Write code

Then the code is created in order to make new test cases successfully pass. This is the main goal of this step.

4. Run tests 

Tests are performed again and until they comply with test requirements. If all tests are successfully passed, software engineers can be reassured that everything is going smoothly. 

5. Code refactoring

Programmers can do code refactoring to receive a shipping solution at the end of the development stage, called a ‘sprint’ (generally a sprint takes 2 weeks). In our company, we regularly clean up and improve the growing codebase along the TDD process to deliver a quality product and simplify its creation. As code refactoring helps receive clean, stable code, it is undoubtedly one of the best software engineering practices.

Cycles of test running and code refactoring are repeated again and again until the desired result is accomplished. Being an ‘Agile’ development methodology, TDD provides a high level of speed and flexibility.

The main advantages of TDD

TDD is another ‘Agile’ development practice that helps deliver quality mobile and web solutions faster and with better results. See the key benefits of TDD below:

  1. TDD facilitates the process of writing clean, reusable code.
  2. TDD enables mobile and web developers to increase product testability.
  3. TDD prevents software engineers from breaking existing product functionality during code refactoring.
  4. This approach lets programmers check each feature and achieve compliance with the project requirements.
  5. TDD provides the ability to get a working product at the end of each sprint and check intermediate results.

Now, let’s consider another popular software engineering practice, called behavior-driven development. It is noteworthy to mention that it evolved from TDD.

What is behavior-driven development? 

 BDD is a software engineering process that focuses on user behavior and employs either general techniques of TDD or principles of domain-driven design. Tests can be prepared in a common language (for instance, English) used by the team so that even non-technical specialists can understand it. The purpose is to encourage communication between programmers, QA, project managers, business analysts—everyone who is involved.

 Just like with TDD, tests in BDD are created prior to code but they are based on the product behavior. Test cases explain how the system should behave which can be done using actual project requirements.

The BDD process generally includes the following steps:

  1. A business person, for example, a product owner, defines the desired behavior of the system. 
  2. The team analyzes the project idea, goal, and requirements to form a clear picture of how the end product should work, how users should interact with it, and what their experience should be like.
  3. Requirements are turned into user stories that specify practical examples—only valid user scenarios are considered.
  4. Automated scripts are written based on user scenarios to run against functional code.
  5. Software engineers write functional code and run new tests. When all the behavioral test cases pass, the solution is ready.
  6. Programmers refactor the code to deliver a shipping product at the end of the sprint.

To make BDD work for you, you should have things such as technical specifications, product behavior, and user needs clearly defined.

The key benefits of BDD

  1. Both TDD and BDD aim to produce a great mobile or web application but BDD focuses on user behavior and interaction with the product. This helps make it work as intended.
  2. Since test cases are created in a common language and by the whole team, BDD improves communication between software and QA engineers, business analyst, project manager, and product owners. As a consequence, everyone clearly understands the customer’s needs and expectations and sees how to implement them technically.
  3. The BDD approach helps development teams to avoid lack of user focus, unnecessary features and makes the interaction with the product intuitive.
  4. As you can see, BDD is focused on user behavior that lets developers ensure that the end product successfully solves the user’s problems and works as intended.

What’s the difference between TDD and BDD?

Although test-driven development and behavior-driven development seem to be quite similar to each other, there are some differences that you should know. Take a look!

  1. In BDD, test cases focus on how users interact with the product and how the app should behave. The TDD approach focuses on testing features and writing quality code.
  2. Changes that are made to product functionality can be adjusted with less influence in BDD as compared to TTD.
  3. In TDD, tests are prepared in a programming language while BDD means the use of a common language that can be understood by each team member.
  4. BDD allows the client, product owner, and everyone in the software development team to have the same picture of project goals and requirements.

 Being focused on different goals, TDD and BDD can be used either in conjunction or separately.  In some cases, to apply only one practice will be enough. BDD perfectly fits for action-driven software systems like e-commerce websites, e-learning, HRM, and loyalty program solutions. Providing the ability to define user behavior, it will let you take into account all the user actions. 

 TDD will be the best choice if you need to develop a product that is poised to have such things as data storage and exchange, third-party API, user bases, and so on.

Final thoughts

 The use of test-driven development and behavior-driven development helps companies deliver quality services. The client can always see intermediate results and make sure the product evolves as needed. Engineers enjoy creating clean code and implementing functionality that meets project requirements and user expectations. TDD and BDD practices also enable teams to reduce the time and costs necessary for building software. 

 If you have questions about this article or want to share your thoughts, please leave your comments below. In addition, we recommend you to read our previous post “Why is QA testing important? How to build a quality product” that explains the role of a QA specialist and describes eight important types of testing.

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