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TDD vs BDD – What’s the Difference Between TDD and BDD?


What’s the Difference Between TDD and BDD?

In the world of software development, we often hear about test-driven development (TDD) and behavior-driven development (BDD), but what exactly is the difference between these terms? If you’re looking for a simple answer to the difference between TDD and BDD, this post from our team of software experts contains everything you need to know.

What is Test-Driven Development?

Test-driven development is a software development process that involves writing tests describing the results you’ll want to see from the changes in the code before any code is written. Ultimately, the aim of using test-driven development is to reduce bugs and improve the maintainability of the project code over time.

Since test-driven development starts with describing the outcome needed from the software, and the tests needed to confirm the software is producing the expected outcome, it often goes hand-in-hand with thought exercises used to design test cases.

Usually, test-driven development also relies heavily on automated tests because the developers regularly run the tests against the code they are developing to track progress towards completion. Once all of the automated tests pass, the developer can confirm that they’ve met the acceptance criteria defined and verified by the tests.

What is Behavior-Driven Development?

Behavior-driven development, same as test-driven development, also begins and is driven by tests. However, the main difference is that in behavior-driven development, the tester is the one who defines the expected software behavior. The outcome is in the form of user stories at a higher level of abstraction (we’ll show you an example shortly).

User stories in behavior-driven development are commonly written using Gherkin syntax. Gherkin syntax structures plain English text so that a machine can later recognize it, in a way that describes a set of inputs and context that exist to produce an expected result.

Here is an example of a task written in Gherkin syntax:
  Given I am on the password reset page
  When I enter "username" or "email address"
  And I click on "Reset password"
  Then I receive a password reset email

Usually, these Gherkin user stories in behavior-driven development are produced as a result of a collaborative effort between product owners, business analysts, developers, and QA teams.

What Are the Main Differences Between TDD and BDD?

While TDD and BDD do share a lot of similarities, they still have some important differences that every time needs to know about to avoid confusion.

One crucial difference is in what TDD and BDD are aiming to test, respectively. While TDD aims to test the software functionality down to specific, smaller pieces in isolation, BDD aims to test the software from the user perspective to ensure a high-level outcome is achieved.

In addition, TDD is usually performed by a software developer in isolation, whereas BDD is normally a collaborative process where several team members from different disciplines write the user stories together.

How Does testRigor Bring BDD to a New Level?

Typical BDD is a 3-step process:
  1. Teams create specifications using the Gherkin language
  2. Engineers develop the desired feature
  3. QA people write automated tests based on Gherkin specifications from step 1

If you’re somewhat familiar with testRigor, you know that you can easily create executable specifications in plain English (which is easier for everyone to understand than Gherkin). So by using testRigor, you can streamline the process and completely eliminate one of the steps.

The process with testRigor looks like this:
  1. Teams create executable specifications in plain English using testRigor
  2. Engineers develop the feature

In the end, testRigor is one of the most powerful tools in the market for any team using a BDD process for their software project. It takes out many of the imperfections of BDD, and saves resources. We’ve created a separate article that further explains the benefits of incorporating testRigor into the BDD framework (we even shaped a new term for it, SDD).

If you’re interested in learning more about how testRigor and BDD can streamline your software development process, get in touch with us and our friendly team of software development experts will gladly show you how your team can get up and running in a short time.