What Is TDD?

TDD stands for Test Driven Development. In this software development technology, we first create test cases, and then write the underlying code of these test cases. Although TDD is a development technique, it can also be used for automation testing development.
Teams that implement TDD need more time to develop, however they often find few defects. TDD improves the quality of code and makes it more reusable and flexible.
TDD also helps achieve high test coverage of about 90-100%. The most challenging thing for testers following TDD is to write their test cases before writing the code.

Process Of TDD

TDD methodology follows a very simple process like below:

  1. Write a test case: Based on the requirements, write an automated test case.
  2. Run all the test cases: Run these automated test cases on the currently environment.
  3. Develop the code for that test cases: If the test case fails, then, write the code to make that test-case work as expected.
  4. Run test cases again: Run the test cases again and check if all the test cases developed so far are implemented.
  5. Refactor your code: This is an optional step. However, it’s important to refactor your code to make it more readable and reusable.
  6. Repeat the steps 1- 5 for new test cases: Repeat the cycle for the other test cases until all the test cases are implemented.

Example Of TDD

Example we need to develop a login function for an application with user name and password fields and a submit button. Here shows how the test scripts look like.

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What Is BDD?

BDD stands for Behavior Driven Development. BDD is an extension of TDD. Instead of writing test cases, we start with writing behaviors. Later, we’ll develop the code that the application needs to perform this behavior.
The scenarios defined in the BDD approach enable developers, testers, and business users to collaborate easily.
When it comes to automated testing, BDD is considered a best practice because it focuses on the behavior of the application rather than the implementation of the code.

Process Of BDD

BDD methodology follows a below process and is very similar to TDD:

  1. Write the behavior of the application: The behavior of an application is written in simple words.
  2. Write the automated scripts: This simple English like language is then converted into programming tests.
  3. Implement the functional code: The functional code underlying the behavior is then implemented.
  4. Check if the behavior is successful: Run the behavior and see if it is successful.
  5. Refactor or organize code: Refactor or organize your code to make it more readable and re-usable.
  6. Repeat the steps 1-5 for new behavior: Repeat the steps to implement more behaviors in your application.

Example Of BDD

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Stands for Test Driven Development. Stands for Behavior Driven Development.
The process starts by writing a test case. The process starts by writing a behavior scenario.
TDD focuses on how the functionality is implemented. BDD focuses on the behavior of an application for the end user.
Test cases are written in a programming language. Scenarios are more readable.
Tests in TDD can only be understood by people with programming knowledge. Tests in BDD can be understood by any person including the ones without any programming knowledge.
Changes in how the application functions impact a lot on the test cases in TDD. BDD scenarios are not much impacted by the functionality changes.6
Collaboration is required only between the developers. Collaboration is required between all the stakeholders.
Some of the tools which support TDD are: JUnit, TestNG, NUnit, etc. Some of the tools which support BDD are SpecFlow, Cucumber, MSpec, etc.


Choosing between TDD and BDD can be tricky. Some people may say that BDD is more suitable for bug detection, while others may say that TDD provides higher code coverage.
Neither methodology is better than the other. It depends on the person and the project team to decide on which methodology to use.