Mar 11th, 2022

Understanding the Differences Between BDD & TDD [Updated]


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People keep discussing and writing about TDD vs. BDD and their differences in software development. Despite tons of blog posts trying to settle the debate once and for all, they stand with little to no success. 

For this reason, we have put together a blog post on TDD vs. BDD explaining it comprehensively. We shall reach the answer in a series of steps. However, we are not sure how this article will get treated, so stay with us till the end.

What is Test-Driven Development- TDD?

Test-Driven Development(TDD) is a common practice for developing simple, maintainable, and well-tested code. The approach states that one should write “implementation code” only if there is a “failing test case.” It is an iterative approach for developing software products where –

  • A failing test case is written,
  • Enough business code is created, which makes the failing test case pass
  • Then if needed, the entire code is refactored.
  • Finally, the entire process is repeated, creating more tests over a period of time. 

What is the Process Of Test-Driven Development -TDD?

  • 1Before working on code, it’s crucial to make sure that your customer understands what you're building or creating. After all, if you don't know how your customers plan on using the software, then it's very likely that no one will actually use it once it's built. Choosing a way for them to report back whether features work or not is an important aspect of this step. Things might get a lot easier to understand with the help of user stories and scenarios, which can be written in various ways such as “When we … Then we should see … So that users will …”
  • 2Write the unit test for your use case. Do this before writing any implementation of the code for the use case. After all of that is done and completed, run your tests to confirm that it fails or works any kinks out. Yes, at first, it will probably fail because you have not yet implemented all of the code needed to successfully complete it.
  • 3The idea behind writing a unit test is so we can confidently know that what we wrote while testing works as intended. If something already exists in our program in some shape or form. In that case, we may be duplicating something and therefore wasting time on opening up a second window just to do one tiny little thing when there might not even be a need for another window, to begin with. It's best to get familiar with how everything works together instead of creating more things just because we want variety or just because someone might think it'd be more fun this way.
  • 4To minimize the amount of code you have to write, write the minimum amount that causes your tests to pass. Once you can consistently run that test and find no bugs, you are ready to move on to writing test cases for the next use case.
  • 5Write a test case that covers each new functionality written in the same way as the first test case. To do this, we need to be able to modify our automated tests as changes are made to our source code.

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Top Key Benefits of Test-Driven Development- TDD

  • 1Design is divided into phases: When using the TDD approach, developers focus on a small batch of code at a time, not moving on to the next bit until they are done with their batch. If written in this manner, the code quality is naturally enhanced, making it easier to discover bugs without much fuss and reuse small portions of code to make new features. This ultimately improves solution architecture. This corresponds to modular software design principles and also teaches developers to keep the code clean.
  • 2Easy maintenance code: Working by necessity with code arranged in a specified order is much easier when changes and modifications need to be made. When developers work according to the test-driven development approach, they naturally produce cleaner, more readable, and more manageable code. Focusing on smaller and more digestible code chunks makes it easier for developers to adhere to test requirements and puts less stress on them, and in turn, makes it easier for them to handle other tasks at hand. Cleaned up original code especially comes in handy when the task or project is transferred to different members of the product team.
  • 3Refactor constantly: It's always a good idea to review your work at the end of each day. One strategy is to run all the tests, see where they fail, and deal with them one by one. When you fix one aspect of a program it can indirectly affect other parts that were previously working fine. Sometimes there are conflicts in these changes, and it may be necessary to make ongoing adjustments between the various tests so that is why making sure you have a robust test environment is so important. The main aim of refactoring code is to improve its ability to tell you — the author — what it’s doing. By getting feedback from the code, we can ensure it works as expected all of the time, every time.
  • 4Project costs decrease and increase in ROI: With test-driven development at the core of your workflow, you can create cheaper software faster. Fewer bugs mean less time spent debugging and building up new features!
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What is Behavior-Driven Development -BDD?

Behavior Driven Development Training (BDD) is a process that promotes collaboration between developers, testers, and customer service personnel during product development.

Process Of BDD

  • Document the behavior of the application: The behavior of the application is documented in simple English by business analysts, QAs, and product owners.
  • Convert into automated scripts: The behavior of the application written in simple English is then converted into programming tests.
  • Apply the functional code: The functional code describing the behavior is then applied.
  • Verify if the behavior is successful: Determine if the behavior is successful. Jump to the next behavior if successful or work if the current behavior has errors and resolve them.
  • Refactor and clean your code: Refactor and filter your code to make it easy to read and understand.

Top Key Benefits of Behavior-Driven Development -BDD

  • 1Addition: Behavior Driven Development (BDD) is a great way to work with product teams to ensure that the right set of requirements is built into the software being developed. BDD borrows heavily from The Three Amigos methodology but guarantees collaboration between customers, business analysts, and developers as they move forward with product development as it is well-embedded in Agile development methodologies like Scrum or Kanban. In essence, BDD is an enhancement of The Three Amigos wherein acceptance criteria are used like integration tests during the development and testing of features by a cross-functional team.
  • 2Transparency: When describing your product’s behavior, scenarios are concise and easy to understand. Each scenario describes a unique aspect of the experience. It makes it easier for the customer to wrap their head around the whole idea in layman's terms, so they can accurately describe what they want when they want it.
  • 3Well-organized: BDD is designed to speed up the development process. Everyone involved in development relies upon the same scenarios. Scenarios are requirements, acceptance criteria, test cases, and test scripts all in one – there is no need to write any other artifact. The modular nature of Gherkin syntax expedites test automation development. Furthermore, scenarios can be used as steps to reproduce failures for defect reports.
  • 4Shift Left: Shift Left is a technique that brings testing earlier in the process. Test early to catch bugs sooner. BDD lends itself well to shift left because TDD and ATDD become part of the requirements definition for traditional waterfall projects or grooming for Agile projects. As soon as behavior scenarios are written, it’s time to start testing and automating.
  • 5Artifacts: The scenarios, which form the test project's finished composition, are like a collection of self-documenting essays documenting each of the various tests that have been taken. This ever-growing collection is perfect for regression testing because they allow anyone assessing the success or failure of a given product to effectively read through an easy-to-follow and well-organized set of instructions on how to accomplish any task and determine whether or not the given product accomplished each step successfully.

Difference between TDD and BDD

Test-Driven Development (TDD)

Behavior-Driven Development (BDD)

Test-Driven Development (TDD) refers to the practice of writing a piece of code only if the automated test has failed. Behavior-Driven Development Training (BDD) is a process that promotes collaboration between developers, testers, and customer service personnel during product development.
Developers are the key participants in TDD Developers, Customers, QAs are the key participants 
Mainly concentrates on unit tests  Mainly concentrates on system requirements 
Point of inception is a test case  Point of inception is a scenario
TDD is a development practice BDD is a team methodology 
Collaboration is limited to developers in TDD Collaboration is required by all stakeholders in BDD


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How They Work Together

Test-first development is a methodology that works very well when paired with Behavior Driven Development. This pairing creates greater emphasis on testing from a developer’s perspective, and it does so in an efficient way by creating different types of unit tests for robust components (that) ensure each component works as expected on its own (and when combined to form applications).


TDD and BDD both serve their purposes. Agile teams should decide what best suits them and use both of them in proportion to reap their benefits. Read the definition, process, and benefits of TDD and BDD which can help you understand the uses of both. 


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