TDD vs. BDD: Choosing The Right Framework

Posted by Ritesh Shetty | July 9, 2021
Automation •

141032 Views | 20 Min Read




The shift to the Agile approach has made a massive impact on the development process over the last decade. A large number of organizations are making a shift to the agile approach, as it helps in shipping a quality product at a faster pace. Continuous testing has now become an integral part of the development process, and this change is here to stay! As a result, the developers can introduce new changes and prevent bugs (or breakdowns) from impeding the scalability of the product.

Organizations that are operative with the Agile development process are familiar with Test-Driven Development (TDD) and Behavior-Driven Development (BDD). These terms do look synonymous but are very different from each other. The battle between TDD vs. BDD is understandable since both approaches are remarkably different from each other. Nevertheless, these processes play an instrumental role in shaping the development work.


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So, how do these terms translate in terms of the depth of test results and robustness of the application (or website)? What are the pros and cons of each approach? Can we use TDD in conjunction with BDD?

This is where the face-off in terms of TDD vs. BDD is important as it will help in arriving at the right decision.

In this blog, we have deep dive into TDD vs. BDD comparison by looking at both these approaches on an individual basis. Later, we would compare them on the lines of functionalities, supported frameworks, and more.

So, let’s get started!

What is Test-Driven Development (TDD)?

Test-driven development or TDD is a testing approach where the Quality Assurance Engineer starts by writing tests for every minute functionality. After designing and writing the test cases, the code is written in accordance with these test scenarios.

Read: 17 Lessons I Learned For Writing Effective Test Cases

At first, the tests might fail if the underlying feature that needs to be tested is not ready. Then, the code is refactored according to the tests till they pass. The intent is that the code should hold the TDD test case, and if it is unable to do that, we rewrite the code again. This enables us to reduce the duplication of implementation in the test scripts to a certain extent.

TDD is a test-first approach that involves the creation of test cases based on pre-specified requirements. The code is then revamped for passing the pre-designed tests. This forms a cycle until all the test scenarios have passed. Once all the test cases are passed, it means that all the functionalities are usable without any bugs (or issues).

Read: Role Of Automation Testing In Agile

The development process with TDD is divided into three major stages:

  1. Red Stage: When there is a need to develop a unit of functionality, we need to break the development process into smaller tasks. Here are the steps that have to be performed in the Red Stage:
    • Define the software functionalities into smaller units in order to break down the development unit into minute features.
    • Create a test for the task and write tests so that the developer focuses on the implementation of the features. Keep the test design super simple and super minimalistic.
    • Run all the tests and check whether the newly created test scenarios fail. This is required to test the newly implemented features in the product.
  2. Green Stage: In the Green Stage, we produce the code for small units of tests created in the Red Stage. Here are the major steps performed in this stage:
    • Write short and simple code for the previously defined test case(s).
    • Test the features by running the tests and verify whether they pass (or fail).
    • Run all the test cases again and make sure that all of them pass.
  3. Refactor Stage: Refactor Stage is used to keep all the tests workable. This is ensured by:
    • Refactoring the code by removing all the issues, thereby ensuring that all the tests are workable.
    • Improving the test code without adding any new code to test further functionalities.

How to Implement Test-Driven Development (TDD)

Test-driven development gives preference to testing instead of the implementation phase. As all the tests pass, it signals the end of the first iteration. However, if more features have to be implemented, all the phases must be repeated with new feature tests. The figure below summarizes the flow of TDD:

Test-Driven Development

Pros and Cons of Test-Driven Development (TDD)

TDD is a test-first approach, where automated test scripts are typically written before implementing the product’s actual features. However, TDD has its own share of advantages (or pros) and disadvantages(or cons)

Advantages of Test-Driven Development (TDD)

  1. Reduced cost of Development: The development process in TDD is divided into smaller chunks to simplify the detection of issues at the early stages of design and development.
  2. Focus on design and architecture: Writing tests before the implementation makes the development process more seamless and efficient.
  3. Improved Code Coverage: Through TDD, a well-designed system can achieve 100 percent code coverage.
  4. Code visibility: Tests are written to verify smaller functionalities, making it easy to refactor and maintain the code.
  5. Detailed Documentation: Since tests are written for verifying micro-level functionalities, writing documentation becomes an easy task.

Disadvantages of Test-Driven Development (TDD)

  1. Bugs leading to faulty code: Tests could contain bugs which in turn results in faulty implementation. This can be averted by using the right BDD framework, performing detailed code review, and more.
  2. Costly Architectural mistakes: If the generated test code is not in line with the desired architecture, it could result in huge losses.
  3. Slowness in development: Creating test cases before code development slows product development. In addition, framing test cases may take a huge time as the actual implementation is not available at that time.
  4. Requires prior experience: Prior experience with TDD is a must since many teams commit the mistake of not running tests at the Red Stage.

What is Behavior-Driven Development (BDD)

Behavior-driven development or BDD is an example-based approach that is derived from TDD. BDD focuses on continuous communication and a shared understanding of the software product amongst the developers and engineers of the development and product teams. This understanding is achieved by creating scenarios of the desired behavior of the product.

The tests focus on the system’s behavior, and features are developed based on these behavioral predictions. The most common approach used in BDD is given-when-then. For example, given a user who enters valid login credentials, the prediction of the next step is when a user completes the login process by clicking the sign-in button, the expected outcome is that a validation message is displayed.

Behavior-Driven Development

Here is the overall approach to BDD:

  1. Discussing Feature(s): The feature is discussed between teams using various approaches like given-when-then, etc.
  2. Writing Scenario(s): A scenario is a user’s story written in plain text using the Gherkin language. You can read our earlier blog on Behaviour Driven Development By Selenium Testing With Gherkin to get more details about Gherkin.

    Gherkin allows the analysts, developers, etc., to describe scenario(s) via the given-when-then format. Scenarios are written so that they describe the behavior of the feature in a comprehensive way.

  3. Code Development: The code (or steps) is then developed based on the scenarios. These scenarios act as acceptance tests on which developers develop code for that particular feature.
  4. Passing the Scenario: Here, same as in TDD, the code for a particular scenario should be the same as the prediction made for it. The acceptance tests are attempted to check and pass the scenarios.
  5. Refactoring of code: The QA team refactor the code if any bug strikes despite the scenario articulation. Thus, the testers work to eliminate bugs from the scenario code by refactoring it.

Read – How To Perform Automation Testing With Cucumber And Nightwatch JS?

How to Implement Behavior-Driven Development (BDD)

As we know, BDD is an extension of TDD. BDD plays a crucial role in cutting back the bugs and errors you would encounter at later stages of product development. Effective test scenarios can be developed by involving different teams (e.g., engineering, product management, marketing, etc.).

Read: All You Need To Know About Automation Testing Life Cycle

The BDD technique accords technical and non-technical teams for the collaboration of knowledge and ideas. It’s time for some action. Let’s look at how to use the BDD framework in Java. We would be using Maven for demonstration. Please check out Maven Tutorial to get started with Selenium Testing in case you are new to Maven.

Step 1: Create Maven Project (adding dependencies).

  1. Open your Eclipse IDE. Click on the File menu, then New>Project.
  2. tdd vs bdd

  3. A new dialog box appears. Select Maven Project and click Next.
  4. chossing the right framework

  5. Click Next to move to Archetype selection.
  6. Select “maven-archetype-quickstart” from the Archetypes listed and click Next.
  7. the right framewrk

  8. Enter the Artifact Id as “bddProject” and click Finish.
  9. bddProject

  10. You will find the project loaded in the package explorer in a few seconds on the left side.
  11. Go to pom.xml of your project and add a few dependencies under the tag <dependencies> in the pom.xml, these are as follows:
  12. The pom.xml will look like this:
  13. All the required dependencies are added to pom.xml.

Step 2: Create a Feature File.

  1. Feature file is a file that narrates the scenario via the Given-When-Then Approach. It’s written in a basic language like Gherkin.
  2. In the project explorer, right-click on the “src/test/java” and create a new package named dataTable.
  3. Enter the name dataTable, and click Finish.
  4. daya tables

  5. In this package, right-click and create a new file named, dataTable.feature.
  6. Enter the name dataTable.feature and click on Finish.
  7. tddvs bdd

  8. Now, we will define the scenario in this file. Copy the below code and then paste it into the dataTable.feature file.
  9. The required feature file is created.

Step 3: Creating a Step Definition File.

  1. The Step Definition file defines how the feature will be implemented as defined in the feature file. Here, it will be a simple Java class file.
  2. To create the Step Definition file, just right-click the package “dataTable,” and select New>Class.
  3. Step Definition File

  4. Enter the name as “StepDefinition.java” and click Finish.
  5. Populate your “StepDefinition.java” with the below code.
  6. Your Step Definition class is ready.

Step 4: Create a Runner File

  1. Create a Java class using the above method, named “RunTest.java.” The Runner class is used to run the tests as defined by the feature file. You can also generate code coverage reports from this Runner class.
  2. Populate the RunTest.java with the following code:
  3. The final hierarchy in the package explorer will look like this:
  4. Now that all the classes and files are created, we will run the Test cases.

Step 5: Run the Project.

  1. To run the Test Cases, select the RunTest.java class and right-click on it. Select Run As>JUnit Test.
  2. RunTest.java will run the test case mentioned in the StepDefinition.java class according to the scenario mentioned in the dataTable.feature. This can be viewed as:
  3. StepDefinition

  4. Scenarios in BDD are developed as tests and run via the Runner class. Thus, in BDD, there is no need to change the entire test implementation in case there are no major changes in the feature file. This is an advantage of BDD over TDD.

Pros and Cons of Behavior-Driven Development (BDD)

BDD is an approach that involves managers, testers, developers, etc., in the whole process. As a result, BDD offers a huge number of benefits. Let’s look at some of the major ones in this section.

Advantages of Behavior-Driven Development (BDD)

  1. Improved Communication: Creating scenarios requires close coordination between clients, managers, developers, testers, etc. This unifies the team in understanding the product behavior.
  2. Reduced cost of Quality Control: Automated acceptance tests are used to depict the scenarios, which in turn helps in reducing the costs involved in inspecting the product quality.
  3. Accurate task estimation: Since the expected behavior is predicted before, there are few chances to change the software application’s architecture.
  4. Better user experience: The scenarios and tests written before development take the user’s perspective into account. The focus is on the desired behavior rather than on the implementation of features.
  5. Excellent documentation: When a certain test fails, the specification is updated, resulting in the detailed documentation.

Disadvantages of Behavior-Driven Development (BDD)

  1. Requires more time than the traditional approach: Putting all the people together becomes difficult for teams. In addition, maintaining test scenarios also requires more time, which results in additional overhead.
  2. Slowness in product development: To create a shared understanding, the management, testing, and development teams must collaborate. BDD adaptation becomes slow if there is no mutual understanding between these divisions within the enterprise.
  3. Suited for large teams and less complex projects: If the team includes a couple of developers who are constantly in touch with testers and project managers, then the development of scenarios can be additional overhead. Doing a detailed analysis between TDD vs. BDD testing and developing test cases before development can be useful for smaller teams.
  4. Implementation is necessary at the beginning of the project: There is no point in developing scenarios between the development process. This will decrease efficiency and make minimal business sense. Also, retrofitting scenarios in legacy systems is nearly impossible.

cross browser testing

TDD vs. BDD – The Final Showdown

TDD vs. BDD is a quest for some developers. Even experienced developers find it difficult to differentiate between these approaches. Now that we have touched upon the working and implementation of TDD and BDD, let’s deep dive into the major differences in this epic TDD vs. BDD clash:

Criteria

Test-Driven Development

(TDD)

Behaviour-Driven Development

(BDD)

Language

Test cases designed in TDD are Technical. These are similar to the test cases that are normally written during the testing phase.

The test scenarios designed in BDD are written in simple English language.

Implementation Level

There is a low-level implementation in TDD.

The scenarios are easy to understand and implement, making BDD a high-level implementation with regard to test case development.

Key Stages

Test case development is the major phase in TDD.

Discussion and creation of scenarios are the major stages in BDD.

Stages involved in Development

TDD involves three main stages, Test creation, implementation, and code refactoring are the major stages in TDD. 

BDD involves a number of stages like feature discussion, scenario creation, testing, implementation, and code refactoring.

Participants

Only technical teams like development teams take part in TDD processes.

BDD involves many teams, right from client to business analysts, testers, developers, etc. 

Primary Focus

Development of required functionality based on test cases is the primary focus in TDD. 

BDD focuses on the correspondence between implemented features and expected behavior.

Documentation

TDD requires documentation for the creation of accurate test cases.

Thrust is laid on documentation creation during the scenario creation process.

Tools

The tools (or frameworks) used in TDD involve JUnit, TestNG, NUnit, etc. These are used to run test cases.

Gherkin is used for writing scenarios in BDD. Cucumber, SpecFlow, Behave, etc., are some of the widely used test automation frameworks.

Applicable Domain

The main focus in TDD is to get appropriate functionality through implementation.

BDD has the defined domain as “Behaviour.” This focuses on the product’s behavior at the end of implementing the product functionality.

Bug Tracking

Bug tracking is easier in TDD, as the tests indicate whether they have passed or failed.

Bug tracking is relatively difficult in BDD, as we only get to know what went wrong in the process. Faulty code is then found and resolved.

So, these were the key differences as far as TDD vs. BDD is concerned. So, make sure to look upon these differences when you have to decide between TDD vs. BDD.

Can TDD and BDD work together?

So far, we have seen what is different as far as TDD vs. BDD is concerned. The best part is that these processes are not mutually exclusive. While it’s not unusual for Agile teams to use one without the other, making these two work together can ensure a higher degree of efficiency in testing use cases, thereby bringing confidence in the performance.

TDD, when used alongside BDD, gives importance to testing from the developer’s perspective, with greater emphasis laid on the application’s behavior. To implement the specifics, developers can create separate testing units to get robust components. This is beneficial since the same component can be used in different places across the software development process.

TDD and BDD

You can use a cloud Selenium Grid like LambdaTest to leverage the capabilities of both TDD and BDD frameworks. LambdaTest is a cross browser testing platform that enables you to run your Selenium test automation scripts on 2000+ different browsers and operating systems online.

LambdaTest integration with tools like Slack, Microsoft Teams, etc., makes discussions between the teams efficient and easy. TDD or BDD, the choice is governed by the individual needs of an application or the enterprise.

The combination of TDD and BDD frameworks can add more value to the software development process. This is where LambdaTest can be beneficial since it can be integrated with major TDD and BDD frameworks.

LambdaTest organized a joint-webinar on SpecFlow – one of the widely used BDD frameworks for web automation testing with Selenium C#. Make sure to check out the recording to gain deeper insights into BDD, TDD, SpecFlow framework, and more.

TDD vs. BDD – Which approach is best for your project?

As seen in the TDD vs. BDD comparison, both frameworks have their share of merits and demerits. Here are some of the essential factors that you need to consider when choosing between TDD vs. BDD:

  1. The size of the team.
  2. The project scope and complexity of the software product.
  3. Your priorities before development (speed of implementation, time of development, desired test coverage, etc.).
  4. Level of communication between teams and team members.

TDD vs. BDD is an ongoing battle, and the best of both worlds should be explored for the betterment of the project. The below-given points underline when TDD or BDD should be used:

  1. TDD fits any project: TDD is a universal approach. Even if the software is designed, developed, and tested by one or two people, they can still implement TDD. This approach mainly focuses on the quality of the unit. However, TDD doesn’t ensure the behavior of a software product correctly, as TDD doesn’t involve stakeholders in the development process.
  2. BDD is for large teams: BDD suits those who work on complex projects. This approach documents the joint understanding of product behavior. BDD acts as a useful project approach for projects that concentrate on user actions in e-commerce, mobile applications, government services, etc.
  3. BDD works for products with predictive results: The Given-when-then approach assumes that the result of each operation can be predicted before development. But, if the project is based on artificial intelligence or machine learning, the predictions can be changed during the learning process. Thus, the Then parameter will get changed, being the Given and When parameter same. Therefore, for such projects, BDD cannot be used.
  4. Presence of Existing Systems: When working on an existing legacy system, it is better to go for BDD, as designing test cases in the middle of the development process can lead to many bugs and inconsistencies. In addition, TDD becomes a very complex task in such projects.
  5. Scope of the Project: TDD vs. BDD contradict each other in their functionality. In TDD, we develop test cases, while in BDD, the concentration is more on behavioral aspects. Thus, it is better to use TDD when the project involves non-behavioral aspects like third-party tools and API-rich projects. BDD, on the other hand, should be used when behavior comes into consideration.

Therefore it’s clear that both TDD and BDD have their places in the development process, according to the requirements. The details outlined in this blog from the TDD vs. BDD point of view will be extremely helpful in choosing the ideal framework for your project.

Conclusion

I hope that this post will help you choose the correct approach for project development in the near future. You can always view the big picture and decide which approach will work best for your software requirements. Whether you choose to implement test-driven development or behavior-driven development, you will require strong QA and testing skills and tools. At LambdaTest, you can find vast experience in testing and working with both of the approaches. You can give a shout, to know more about our expertise.

Read: 17 Skills Of Highly Effective Software Testers

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Apart from the points above, if you have something to add, we welcome your suggestions. I hope that this post will help shape your testing and development process for your next project.

Thus, till then, Happy Testing!

Frequently Asked Questions

Which one is better: BDD or TDD?

That question implies that Test Driven Development and Behavior Driven Development address the same problem or are mutually exclusive. Instead, they address slightly different issues, and a good route is to use both approaches.

Use Behavior-Driven Development (BDD) to address the needs of business stakeholders and technical teams to understand each other’s perspectives early in the development process. Use Test-Driven Development (TDD) to make sure you’ve built all the necessary functionality required by developers and testers alike.

Why is BDD better than TDD?

There is no argument that TDD is a great way to ensure your code works as intended. However, BDD is seen as an even better practice by many. Using clearer language in the scenarios and test cases and better collaboration between the QA department and the developers created an even higher quality product overall.

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