TDD vs. BDD: What’s the Difference?

Mar 1, 2023 | Programming

TDD (test driven development) and BDD (behavior driven development) are unique software development techniques that differ in what they are testing and how they are testing it. Despite their similar names, they serve distinct purposes.

What Is TDD?

TDD stands for test driven development. TDD is the process of writing a test for a specific portion of functionality, allowing the test to run to determine failures, and then adjusting the code as necessary to remedy the failures. Using these tests, developers can ensure that they’ve written functional, dependable code. Additionally, if other developers need to use components of the code, they can run tests to confirm their code’s functionality.

TDD Process

There are several steps taken to execute test driven development:

  1. The developer writes automated test cases to test the lines of code. 
  2. These tests are then executed to determine the location of any failures in the program.
  3. Changes are subsequently applied (refactoring) to ensure that the failures are corrected and do not occur again in the future.
  4. Finally, tests are executed again until they are passed without error.

Benefits of TDD

There are many benefits to using TDD instead of another style of development, such as:

  • Rework time reduced: Test driven development does not allow new code to be written unless the existing code is successfully tested without failures. Until the failures are completely addressed and removed, the process of writing code is halted. Therefore, time spent reworking broken code is kept at a minimum.
  • Quick feedback: As the tests focus on specific sections of code at a time, developers can receive more immediate feedback that allows them to implement changes more quickly.
  • Increased development productivity: With TDD, the focus is on the production of functional code rather than test case design. As such, productivity increases, and development moves along smoothly.
  • More flexible, maintainable code: Because every part of the code is tested before moving on to the next part of the software development process, the code maintains functionality and is adaptable in the future.

Test Driven Development Example

To better understand how test driven development works in development, it’s helpful to go through an example. In this instance, we can define a class password to meet the condition that it must be 5–10 characters. 

Your first step would be to write the code that fulfills the necessary requirements. Then you run the tests to ensure that the code is valid. For example, you create a class to test the password length, run the test, and then check to see if the output is true or false according to the conditions that you set—whether or not the length of the password is 5–10 characters. If the test returns false, then you can adjust the code as necessary.

What Is BDD?

BDD stands for behavior driven development, and it is a way for teams of software developers and others to work together to narrow the distance between the business-focused team members and technical-focused people through:

  • Encouragement of teamwork across roles to increase understanding of what the problem at hand is
  • The use of rapid, small iterations of work done to advance feedback and enhance value flow
  • Producing system documentation that is automatically checked against the system’s behavior

BDD typically involves the software developers, test engineers, and project managers as well as other stakeholders. This group collaborates to develop concrete examples of acceptance criteria in a user story. Using a domain-specific language, these examples are then described and put into a feature file. This feature file is subsequently converted into a specification that can be executed, thereby allowing developers to write actual tests that can also be executed.

BDD Process

The steps to behavior driven development are fairly simple and repeatable as necessary:

  1. Behavior is described typically by utilizing a user story. This allows the team to discuss concrete examples of the new functionality so that everyone can agree on the expectations of the behavior.
  2. Action is then written by turning the examples into documentation in such a way that it can be automated.
  3. The test is executed to assist the developers and guide them through the development of the code.
  4. The code is then created to make the action pass and make the code functional. 

Benefits of BDD

There are several benefits to making use of BDD for software development, including:

  • Incorporation of user experience: BDD focuses on the users’ experience and, as such, allows the team to develop a broader perspective and make note of gaps in their understanding. 
  • Cost-effectiveness: Because BDD sets priorities for users, developers, and investors alike, it allows for resources to be used optimally in the development of programs.
  • Simple cross-browser testing: BDD focuses on behavior, which means that it gives you an ideal framework for cross-browser testing.

Behavior Driven Development Example

Behavior driven development follows the “Given-when-then” framework. For example, if your site has a language translation feature and provides translations of the entire webpage in Italian, Spanish, and French, you could encounter scenarios such as the following:

  • Scenario: Receive Messages in my Set Language (Italian)
    • Given I am the user “fmallo”
    • When the system sends the message “Invalid Login”
    • Then I should see the error message “Login non valido”
  • Scenario: Change the language I use
    • Given I am the user “dmessina”
    • When I set my language to “Spanish”
    • Then my language should be equal to “Spanish”

Difference Between TDD and BDD

The primary differences between TDD and BDD lie in what is being tested and how. BDD predominantly focuses on the end user’s standpoint in its testing of the application behavior, whereas TDD focuses on smaller sections of functionality to be tested by itself.

Additionally, BDD involves a larger group of people—project managers, developers, and test engineers who come together to develop the behavior examples. As such, a great deal of communication is needed before anything is implemented. On the other hand, TDD can be done by a sole developer without external input from project managers or stakeholders.

Using Ranorex for Behavior Driven Development

Ranorex DesignWise has been built for a BDD framework. With DesignWise, you can create tests faster with less redundancy, less risk, and less coding. Then, you can important them into Ranorex Studio to run the BDD tests.

Using Ranorex for Test Driven Development

If test driven development is more suited for your project, Ranorex also has you covered. Whether you want to conduct functional testing or regression testing or any number of developer-led testing for your TDD, Ranorex Studio presents you with the ideal platform to automate all of your testing.

Improve Testing Automation with Ranorex

Ranorex Studio is a versatile and powerful tool for developers and novices alike, with an array of features that allow you to create and run tests without the need for complex coding or manual testing. If you would like to test it out for yourself, you can contact us for a free trial of Ranorex Studio today.

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