BDD vs. TDD: What Are They and How Do They Differ?

Organizations shifting to agile have made a huge impact on their software development processes over a decade, the core reason being fast-paced delivery for a quality product. The term ‘Continuous Testing’ is known to be a crucial component in this phase. As they rightly said, change is the only constant, this change agile has brought along is here to stay!

What are you evaluating?

BDD is intended for testing the behavior of an application’s behavior from the end user’s point of view, whereas TDD is designed to test isolated pieces of functionality. Thus, when we compare bdd vs tdd, the TDD test asserts the outcome of a particular method, whereas the BDD test is only concerned with the result of a higher-level scenario.

It’s very important for teams operating in agile to be well aware of TDD and BDD. Even though they look similar, they are way more different from each other.

BDD eases the collaboration between important stakeholders such as product developers, test engineers, and managers. This form of communication is important at every stage of implementation. On the other hand, TDD is a form of development that can be carried out entirely by a solo developer without any assistance from product managers.

In both cases, the code required to pass the test is written by the developer. These tests can also be a part of an automated testing framework to identify and correct the issues even before they are actually introduced in the application.

Let us understand in detail what impact it makes in shaping the development!

TDD is known as Test-Driven Development: This entails writing a test that fails due to the absence of the specified functionality, then writing the simplest code possible, followed by refactoring to eliminate duplication, and so forth. You repeat this Red-Green-Refactor loop indefinitely until the feature is complete.

BDD is known as Behavior-Driven Development: This entails creating an executable specification that fails due to the absence of a feature and then writing the most straightforward code possible to make the specification pass. This process is repeated until a release candidate is ready for shipping.

Those appear to be quite similar, don’t they? The critical distinction is in the scope. TDD is a technique for developing software, whereas BDD is a team methodology. In TDD, developers write the tests, whereas, in BDD, users or testers create the automated specifications (with developers wiring them to the code under test.) Nevertheless, TDD and BDD are effectively identical in small, co-located, developer-centric teams. 

Software Development

Collaboration between the two

BDD entails collaboration between developers, testers and generating substantial examples of expected functionality. Thus, before any implementation, there is extensive communication. In comparison, TDD frameworks can be performed independently by a single developer without the involvement of any related stakeholders, more importantly, product managers.

How Do They Interact – BDD vs. TDD?

It’s critical to understand that the two models are not mutually exclusive — many agile teams prefer TDD exclusively. However, BDD makes sure that most of the application’s use cases operate at the top level, providing  greater confidence.

BDD can be used, for instance, by a development team to create higher-level tests that verify the functionality of an application. However, developers may create the unit tests separately to check the components’ robustness when implementing the specifics, particularly given that these components can be reused throughout the application.

Disparities in Implementation

Agile development firms have widely adopted test-driven development, and there are numerous tools available to assist teams in getting on the same page. Unfortunately, because behavior-driven development requires communication between business and technical teams, it is sometimes difficult for the teams to get the feasible tools that suit their requirements.

BDD test management tools bridge the gap and simplify continuous testing. Simple-to-use scenario editors enable business teams to quickly define and update features, while integrations with automation frameworks and continuous integration/continuous delivery pipelines simplify test writing. 

The plain-text language used in the features and the aggregated data from the integrations contribute to creating living documentation that technical and business teams can refer to at any time. 

For instance, business users can verify that a particular feature was developed and functional in the recent CI run.

The good news is that BDD does not require any changes to existing TDD practices; it simply requires an investment in more communication, which can pay off in less ambiguity and increased confidence in the product.

The Verdict

Over the last several years, test-driven development has become the de facto standard approach for agile software development. This approach minimizes the number of bugs that make it into production and ensures that software can be released without interruption.

Behavior-driven development is an evolution beyond test-driven development where business goals can be communicated to developers more effectively. By bridging the gap between business and technical teams, BDD helps eliminate confusion about acceptance criteria, early identification of potential issues with user stories, and ensure that the application functions as expected for end-users.

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