Test Driven Development vs. Behavior Driven Development

June 15, 2017

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Uttam B Ramamurthy

Practice Head - DevOps

Test-driven development (TDD) is also known as test-driven design. It is a method of implementing software programming that works with unit testing, programming and refactoring on source code.

TDD – Test Driven Development technique works with automated test cases prior to writing the code. It is practiced popularly with Agile Methodologies since it helps in developing a deliverable at the end of every sprint.

The Test cases in TDD are written in programming languages such as Java, Ruby, etc. The popularly used tools in TDD are test automation tools such as Selenium, Watir, Windmill, etc.

TDD involves the following steps:

  • As per the decided requirements in the documents, test cases will be written by the developer
  • These tests are run and since they do not have any implemented features, they fail
  • After this, the developer performs testing once the code is written
  • After getting a green light from the test script, the development team can refactor and organize the code to achieve a deliverable at the end of a Sprint

Behavior Driven Development (BDD) is a Software Development technique that helps in defining the behavior before writing the Test Automation scripts or functional code pieces. In an Agile sprint process, it results in a deliverable product at the end of every sprint.

This consists of the following steps:

  • A Product Owner will define the behavior of the user in simple stories
  • These stories are then detailed as Automated scripts that will run with functional code
  • The functional code is then written by the development team to receive a go-ahead from the automated test script
  • The code can then be refactored and organized by the development team to achieve a deliverable at the end of the sprint

Different tools including Cucumber, FitNesse, PowerTools, Docker, etc. are used in BDD. The test scripts are written in simple and lucid English with Gherkin, Wiki frameworks, etc. This practice helps the stakeholders to be involved in the process. Moreover, a simplified user story helps reduce the risks involved in developing code that cannot meet the accepted user behavior.

Test Driven Development (TDD) vs. Behavior Driven Development (BDD):

  • BDD has a simplified and lucid English format that the stakeholders can comprehend and be involved. TDD on the other hand uses programming languages such as Ruby, Java etc. to write test cases
  • BDD details the behavior of the application from end user point of view. TDD focusses on the implementation of the required functionality. Any change in the functionality accommodates less impact on BDD as compared to TDD
  • BDD makes it possible for the stakeholders to be involved in the process and therefore improves the accuracy in meeting the requirements. This however is not that easy when it comes to TDD


BDD revolves around the idea of a behavior driven application. The focus in this case, is on the customer requirements and the onus is on the developers to meet it. Therefore, the testers in this process get to play as customers. If certain actions do not have any effect on the end user, BDD may not be able to serve its intended purpose. TDD, on the other hand is perfect for such scenarios.

There are many Software Development practices that are followed across industry domains. It is not possible to define a single practice that can be uniformly beneficial to all projects and processes. BDD is a good medium in capturing user actions in case of systems that are oriented towards end user actions. The best example for this is an ecommerce website or a HR application. TDD is the best suited solution wherever systems include third party API calls, Cron jobs, data exports/imports, etc.

The choice however, between TDD and BDD is rather complex. The selection depends on the testing framework suitable for the given language and comfort and willingness of the development teams, among other factors. There is always a stated argument that BDD is better that TDD. The popular reason being that BDD has the capacity to eliminate issues that can come up during TDD.

This could be true but not always. Issues in the likes of poor co-ordination and design practices will continue to persist. The major change will be in the way of a lower likelihood of writing bad test cases, which in turn can fetch stronger results.

Neither of the styles are better than the other in comparison, it all depends on the utility and the context.

Finding a partner for TDD and BDD:

Finding a suited partner in Software Development for TDD and BDD is very important. Nous Infosystems, with its skilled resources and ability to adapt to different development approaches, has expertise in test-driven and behavior-driven development.

If you would like to know more about our DevOps Consulting Services, then do get in touch with us.

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