Unleashing the Testing Battle: TDD vs BDD - Which One is Right for Your Development Process?

During the last decade; the software development industry has shifted from a waterfall model to an Agile one. Since Agile development involves making changes all the time, testing is more important than ever to make sure that these changes don't introduce new bugs or, worse, break the app in production.

Most developers know about test-driven development or TDD, but behavior-driven development, or BDD, is often misunderstood. In reality, both of these ways have pros and cons that you should think about.

In this article, we'll look at TDD and BDD, find out what makes them different, and see how they can work together.

People often get confused about behavior-driven development, but it's just the next step after test-driven development.

What does TDD mean?

Test-driven development is a software development approach that includes building tests that describe the desired outcomes of code modifications prior to writing the code. Test-driven development's ultimate goal is to eliminate defects and increase the maintainability of the project code over time.

Automation testing goals and objectives are important for your testing processes. Check out our blog post!

While test-driven development begins with specifying the desired output of the program and the tests required to verify that the software is generating the desired end, it is often accompanied by mental exercises used to construct test cases.

For how to create test cases for automated tests?

Typically, test-driven development also significantly depends on automated tests since developers often execute the tests against the code they are producing to monitor its progress toward completion. After all automated tests pass, the developer may certify that the application meets the acceptance criteria specified and validated by the tests.

Process of TDD

The process of Test-Driven Development involves the following steps:

1. Write a test: The developer writes a test that will verify a small piece of functionality or a single unit of code.
2. Run the test: The developer runs the test and expects it to fail since the code for that particular function has not yet been written.
3. Write the code: The developer writes the code necessary to pass the test.
4. Run the test again: The developer reruns the test and expects it to pass this time since the code has been written to satisfy the test.
5. Refactor: The developer refactors the code to ensure it is clean and optimized without changing its functionality.
6. Repeat: The process is repeated for each small piece of functionality or unit of code until the overall application is complete.

By following this process, TDD ensures that each piece of code is thoroughly tested and that any issues or bugs are identified and resolved early on in the development process.

Key Benefits of TDD

TDD helps to ensure that software is delivered with higher quality, fewer defects, and greater confidence in its functionality. It encourages collaboration and critical thinking, leading to more efficient and effective solutions.

Improved code quality

It promotes writing code that is modular, easy to understand, and maintainable, resulting in better overall code quality.

Faster feedback

TDD provides immediate feedback on whether code changes are successful, allowing for faster iteration and problem-solving.

Reduced defects

TDD helps to identify defects early in the development cycle, reducing the number of defects in the final product.

Greater confidence

It provides greater confidence in the functionality and reliability of the code, reducing the likelihood of bugs and errors.

What does BDD mean?

Behavioral-Driven Development (BDD) is a testing approach that stems from the Test-Driven Development methodology. In BDD, tests focus mainly on the behavior of the system. This approach provides various ways to develop a feature based on its behavior, often using the Given-When-Then structure when writing test cases. 

For instance, given that the user enters valid login credentials, when they click on the login button, then a successful validation message is displayed.

You can also read 5 Failures in Test Automation: Best Practices for Dealing with Them

The primary goal of BDD is to create an executable specification that initially fails because the feature doesn't exist. Then, developers can write the simplest code that will make the specification pass and implement the required behavior in the system. BDD is a team methodology that involves collaboration between developers, customers, and QAs.

So, BDD focuses on system behavior and encourages teamwork, while TDD mainly focuses on testing individual code units.

Read Also: Smoke Testing vs Regression Testing: Key Differences

Process of BDD

The methodology of BDD involves six steps, which bear a striking resemblance to those of TDD.

Write the behavior of the application.

In this step, the behavior of the application is written in a simple and easy-to-understand English-like language. This is typically done by the product owner or business analyst or quality assurance team to ensure that the application meets the business requirements and the expected behavior.

Write the automated scripts.

After the behavior is written, the development team then writes automated scripts based on the behavior, using a structured format such as Given-When-Then. These scripts are written in a programming language and can be executed to test the functionality of the application.

Implement the functional code

Once the automated scripts are written, the functional code underlying the behavior is implemented. This means that the developers write code to ensure that the application behaves as described in the behavior.

Check if the behavior is successful, and if not, fix it:

In this step, the automated scripts are executed to check whether the implemented functionality meets the expected behavior. If the behavior is unsuccessful, the development team then debugs and fixes any issues in the functional code to achieve the desired behavior.

Refactor or organize code.

After the code is written and tested, it may be refactored or organized to make it more readable, maintainable, and reusable. This step is important as it ensures that the code is easy to understand and modify in the future.

Repeat steps 1-5 for new behavior.

Finally, the process is repeated for new behaviors that must be implemented in the application. This ensures that the application meets all the business requirements and the expected behavior.

Benefits of BDD 

BDD helps to deliver high-quality software that meets the needs of the business and the customer by promoting collaboration, efficiency, and clarity.

Improved collaboration 

It promotes collaboration between developers, testers, and business stakeholders by ensuring that everyone has a clear understanding of what needs to be built and how it should behave.

Increased efficiency

BDD reduces the amount of rework required by catching issues early in the development process, saving time and effort.

Better test coverage

BDD ensures that tests are focused on the most critical aspects of the system's behavior, resulting in better test coverage and fewer defects.

Improved code quality

It encourages the creation of clean, maintainable code that is easier to understand and modify, leading to higher-quality software.

Increased customer satisfaction

BDD ensures that the system meets the customer's expectations by focusing on the behavior of the system, leading to higher customer satisfaction.

What's the Difference Between TDD and BDD?

Asking, "What is the purpose of your testing?" is a crucial inquiry. Do you want to understand how the application behaves or are you more interested in its implementation? This is often the central discussion point when comparing TDD and BDD. 

Curious about the principle of software testing?

TDD involves creating a test method that verifies certain states, but these tests may produce inaccurate results as the system evolves. In contrast, BDD focuses on behavior, such as how the system will react under specific circumstances.
To put it simply, TDD prioritizes the testing process rather than the output. The tests must be conducted in a specific way. On the other hand, BDD emphasizes the importance of the output, which must be correct for the given conditions, regardless of how it was obtained.

Here's a table outlining the main differences between BDD and TDD:

How do TDD Tests Work?

Test-Driven Development is a software development approach where developers write automated tests for a feature before writing the code to implement that feature. The tests are designed to fail initially since the code to implement the feature has not yet been written. Once the tests are in place, the developer writes the code to make the tests pass and then refactors the code as necessary.

The idea behind TDD is to ensure that the code being developed is correct and meets the requirements by having automated tests in place that can quickly catch any regressions or defects. By writing tests first, developers are forced to consider the requirements of the feature before writing the code to implement it. This can help catch potential issues early in the development process before they become more difficult and expensive to fix.

See Also: Unit Testing vs Functional Testing: A Detailed Comparison

How do BDD Tests Work?

Behavior-Driven Development tests work by defining the expected behavior of a system in a natural language that is easily understandable by all stakeholders, including developers, testers, and business analysts. This is typically done using a Given-When-Then format, where each scenario is broken down into three parts:

• Given: This describes the initial state of the system, such as the inputs and conditions required for the test.
• When: This describes the action being performed on the system, such as a user interaction or an API request.
• Then: This describes the expected outcome or result of the action, such as a UI change or a specific response code.

BDD tests are often written in collaboration between developers, testers, and business analysts, ensuring that all parties have a shared understanding of the expected behavior of the system. These tests can be automated using various testing frameworks, which can interpret the natural language descriptions and execute the tests accordingly.

Read Also: Test Planning: The A-to-Z Guide

How They Work Together

BDD and TDD can work together in an Agile development process. BDD provides a way to describe the expected behavior of the application and its features in clear and concise language that can be understood by all members of the development team, including business stakeholders. 

For how to select a test automation service provider?

These specifications can then be used to drive the creation of TDD tests, which are more focused on the implementation details of the code.

In this way, BDD can provide a higher-level view of the application's behavior and ensure that all use cases are covered. In contrast, TDD can provide a more fine-grained view of the code's behavior and ensure its robustness and correctness. 

By using both approaches in conjunction, development teams can achieve a more comprehensive testing strategy that covers both the behavior and implementation aspects of the code.

See More: 10+ Best Software Testing Books in 2023

TDD or BDD? Conclusion

Whether to use TDD or BDD depends on the specific needs and requirements of the project. Both approaches have their benefits and drawbacks, and some teams may choose to use both in combination.

TDD is often used when the focus is on verifying the functionality of the code and catching errors early in the development process. It can help to reduce the time and cost of fixing defects later on in the development process.

BDD, on the other hand, focuses on ensuring that the system behaves as expected by its stakeholders. It helps to facilitate collaboration between different team members and stakeholders, and ensures that everyone is on the same page in terms of what needs to be delivered.

FAQ

Which is better TDD or BDD?

The choice between TDD and BDD will depend on the specific requirements of the project and the preferences of the development team. In some cases, a combination of both approaches may be the most effective approach to ensure that the code is functional and meets the needs of the stakeholders.

References

Browser Stack - TDD vs BDD 

Software Testing Help - TDD vs BDD 

Plural Sight - TDD vs BDD