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Home Guide TDD vs BDD vs ATDD : Key Differences

TDD vs BDD vs ATDD : Key Differences

By Jash Unadkat, Community Contributor -

This guidepost aims to describe different testing methods or practices like Behavioral Driven Development (BDD), Test-Driven Development (TDD), and Acceptance Test-Driven Development (ATDD). It will also help clarify the key differences between these techniques. By the end of this article, one is expected to understand how each method works, its key differences, and its particular roles in the development process.

First, let’s start with the difference between TDD and BDD and then move on to ATDD.

What is Test-Driven Development (TDD)?

Test-Driven Development is a testing methodology or a programming practice implemented from a developer’s perspective. In this technique, a QA engineer starts designing and writing test cases for every small functionality of an application. This technique attempts to answer a simple question – Is the code valid?

The main intention of this technique is to modify or write a fresh code only when the test fails. Hence it results in lesser duplication of test scripts. This technique is prevalent mainly in agile development ecosystems. In a TDD approach, automated test scripts are written before functional pieces of code. The TDD methodology involves the following steps:

  1. A developer writes an automated test case based on the requirements specified in the documents.
  2. These tests are executed, and in some cases, they fail as they are developed before the development of an actual feature.
  3. The development team then re-factors the code for the test to pass successfully.
  4. TDD can be done by a single developer while writing both tests and application code side by side to complete a feature.

Refactoring refers to modifying the code without changing its main functionality or behavior.


What is the main question asked in a TDD approach?

Benefits of TDD

  • Reduces the amount of time required for rework
  • Explores bugs or errors very quickly
  • Faster feedback
  • Encourages the development of cleaner and better designs
  • Enhances the productivity of the programmer
  • Allows any team member to start working on the code without a specific team member. This encourages knowledge-sharing and collaboration.
  • It gives the programmer confidence to change an application’s large architecture quickly.
  • Results in the creation of extensive code that is flexible and easy to maintain

Now, let’s understand everything about Behavioral-Driven Development.

What is Behavioral-Driven Development (BDD)?

Behavioral-Driven Development (BDD) is a testing approach derived from the Test-Driven Development (TDD) methodology. In BDD, tests are mainly based on systems behavior. This approach defines various ways to develop a feature based on its behavior. In most cases, the Given-When-Then approach is used for writing test cases. Let’s take an example for a better understanding of TDD vs BDD:

  • Given the user has entered valid login credentials
  • When a user clicks on the login button
  • Then display the successful validation message

As shown above, the behavior is illustrated in a very simple English language, a shared language. This helps everyone in the team responsible for development to understand the feature behavior.

For example, as shown in the video, one can try running an easy cross-browser test based on a set of instructions to test across multiple devices.

TDD vs BDD vs ATDD : Key Differences

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Key benefits of BDD

  • Helps reach a wider audience through the usage of non-technical language
  • Focuses on how the system should behave from the customer’s and the developer’s perspective
  • BDD is a cost-effective technique
  • Reduces efforts needed to verify any post-deployment defects

The image below depicts a typical BDD operation:

Lifecycle of BDD

In BDD, tests are based on:

How does BDD streamline SDLC?

Debugging the errors in the latter stages of the development life cycle often proves very expensive. In most cases, ambiguity in understanding the requirements is the root cause. One needs to ensure that all the development efforts remain aligned toward fulfilling pre-determined requirements. When it comes to behavior-driven development vs TDD, BDD allows developers to do the above by :

  • Allowing the requirements to be defined in a standard approach using simple English
  • Providing several ways to illustrate real-world scenarios for understanding requirements
  • Providing a platform that enables the tech and non-tech teams to collaborate and understand the requirements

What is Acceptance Test-Driven development?

In the Acceptance Test-Driven Development (ATDD) technique, a single acceptance test is written from the user’s perspective, mainly focusing on satisfying the system’s functional behavior. This technique attempts to answer the question – Is the code working as expected?

Note: Acceptance Test-Driven Development is very similar to Behavioral-Driven Development. However, a key difference between them is: BDD focuses more on the behavior of the feature, whereas ATDD focuses on capturing the precise requirements.

This technique enhances collaboration among developers, users, and QAs with a shared focus on defining the acceptance criteria. The following are some of the key practices in ATDD:

  • Analyzing and discussing the real-world scenarios
  • Deciding the acceptance criteria for those test scenarios
  • Automating the acceptance of test cases
  • Focusing on the development of those requirement cases
ATDD creates acceptance tests from the perspective of the:

Benefits of ATDD

  • Requirements are very clearly analyzed without any ambiguity
  • Encourages collaboration among cross-team members
  • The acceptance test serves as a guide for the software development process

Key Differences: TDD vs BDD vs ATDD

DefinitionTDD is a development technique that focuses more on the implementation of a featureBDD is a development technique that focuses on the system’s behaviorATDD is a technique similar to BDD, focusing more on capturing the requirements
ParticipantsDeveloperDevelopers, Customers, QAsDevelopers, Customers, QAs
Language usedWritten in a language similar to the one used for feature development (Eg. Java, Python, etc)Simple English, (Gherkin) Simple English, Gherkin 
Main FocusUnit TestsUnderstanding RequirementsWriting Acceptance Tests
Tools usedJDave, Cucumber, JBehave, SpecFlow, BeanSpec, Gherkin Concordian, FitNesse, Jest, Jasmine, ProtractorGherkin, Dave, Cucumber, JBehave, Spec Flow, BeanSpec, Concordian, CypressTestNG, FitNesse, EasyB, Spectacular, Concordian, Thucydides, Robot

Understanding how these methods work can help developers and other individuals involved in software development determine which testing strategies best serve their purpose. Depending on the kind of project and the results it aims to achieve, a suitable method (or even a mix of methods) can be deployed to meet specific requirements in the most efficient ways.

TDD vs BDD vs ATDD : Key Differences

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