TDD vs BDD: Test Driven Development vs Behavior Driven Development

If you have been a software developer for some time now, you must have witnessed the tussle that programmers around you face between TDD vs BDD. Well, if you feel completely lost and can’t understand what the fuss is all about, you have come to the right place. To understand the differences and the utility of each, you need to begin by exploring the basics of both. To put it simply, TDD & BDD are two alternate processes to automate your JavaScript programming and testing. Making a choice and tilting towards one is a tricky decision as it requires you to consider multiple factors. Fortunately, we are here to help you make that choice by pointing out the differences and the strengths of each.

TDD vs BDD- The Basics?

Test Driven Development or TDD is a process of writing and running tests to achieve automation. The process begins by writing a test prior to writing the actual code. TDD is most popular amongst Agile Methodologies. Developers generally use Java or Ruby to power TDD. What makes TDD extremely popular amongst developers is a deliverable at the end of every sprint.

Behavior Driven Development is a process of writing and running tests with a prior understanding of user behavior. While it resembles TDD in writing the test before the functional code, it has a step before it too. BDD generally begins by developing a user profile built through user behavior mapping. Popular in an Agile sprint, BDD leads to the development of a deliverable product.

The Objective

If you wish to truly understand which process, between TDD vs BDD, is most suitable for you, you should begin by understanding the objective of each.

BDD attempts to create a series of tests to test a code’s viability in a multiplicity of circumstances. This simply means that BDD is circumstance driven. It focuses less on the output in general and more on the output in a particular condition.

TDD, on the other side, is, as the name suggests, test driven, it is more focused on the implementation than having a situational baggage. Its emphasis is more on the way the test is conducted rather than securing output in a given condition.

To cut a long story short, the objective of BDD is to illustrate an application’s behavior for the end user and make sure it is pleasant. On the contrary, TDD emphasizes on the functionality implementation.

The Design

When it comes to the design element of these approaches, they are more or less very similar. Both of them begin by writing and running of tests before the writing of the actual functional code. This strategy gives developers an upper edge while software development. By identifying the tests that have to be implemented, developers can make sure that they don’t miss out on any element of the code. Additionally, these approaches are particularly useful for the prevention of bugs during software development. Finally, the tests act as a foundational base for documenting what has to be achieved through the test coverage.

The Process

Now that you have some clarity in terms of understanding the basic meaning of TDD and BDD, it is time to explore the difference in processes.

Test-driven development begins by writing a test before the functional code. As expected, writing is followed by running against what is already developed. These tests invariably fail as they haven’t been implemented. What follows running and failing of tests is the creation and deployment of a basic functional code. This functional code generally intends to ensure that the test passes. Invariably, the next step is to run the test again to make sure it works. Once the test script gives a way forward signal, the development team is all free to refactor and organize the code. The end result is a tested deliverable at the end of a sprint.

While BDD also follows a similar path, the reliance on user behavior is exceptionally high. The process begins with defining user behavior through QA surveys, business analyst surveys or other forms of data collection. Powered with user behavior, its conversion to automated testing scripts takes place. Once these automated test scripts are in place, the development team crunches a functional code. Upon receiving the green signal from the automated test script, the development team refactors and organizes the code.

As visible, the major difference in the process of TDD vs BDD is in terms of defining and adapting user behavior.

TDD vs BDD- What is more customer friendly?

The customer friendliness of any process depends on its ease of comprehension by the users. While both the processes are up to the mark when it comes to their utility for customers, their ease of use differs to a certain extent.

Behavior in BDD is written in simple plain English which makes it easily comprehensible by the users. This accelerates the process for users to understand the tests and give quick feedback. This simplicity of communication gives you a wider audience to reach out to. Additionally, this open doors for more transparent communication between you and your audience as its ease of understanding prevent misunderstanding.

TDD, on the other hand, is written in complex programming languages that are definitely more difficult to understand. Comprehension of TDD tests requires technical knowledge of programming skills. While it is true that there is an abundance of users with technical acumen, however, it limits the demographic of the outreach. Simply put, the use of complex programming language in TDD constrains the scope of reaching out to a wider audience. This invariably limits the feedback to a certain set of users, and may not cater to the needs of certain groups.

To sum it up, the ease of comprehension of BDD makes it a more customer-driven process than TDD.

The Developer’s Side

One important thing that deserves due consideration while deciding between test-driven development and behavior driven development, is the developer’s comfort.

As discusses above, TDD is more technologically complex and therefore, the developer’s and testers should be technically sound and proficient. They should not only have the requisite knowledge but also have an understanding of the different programming languages that may come in handy from time to time. Additionally, in TDD software development and testing go hand- in- hand. Therefore, both developers and testers need to have basic knowledge about each other’s work to ensure seamless delivery.

BDD, on the other hand, is relatively simple to work with. Owing to its dependence on simple languages rather than technically complex whereabouts, it is easier to work with. Undoubtedly, developers and testers need expert technical knowledge. Fortunately, they may be able to get away from the complex nitty gritty.

TDD vs BDD- What is the Right Choice?

It is not advisable to mark either of these two processes as a universal right choice. The approach needs appropriate customization based on the product need, team capacity as well as the end user expectation. Each one has its own benefits and it is only your requirement that may be able to determine what suits you the best. Fortunately, each point mentioned above will help you make an informed decision.


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