Test-Driven Development (TDD) and Behavior-Driven Development (BDD); the difference between them.

Test-Driven Development; This Is a software development approach in which you develop test cases to specify and validate what the code should do. In simple terms, you create test cases for each functionality first and then if the test fails then the new code is written to pass the test. This makes code simple and bug-free. Test-Driven Development starts with designing and developing tests for every small functionality of an application. TDD framework instructs developers to write new code only if an automated test has failed. This avoids duplication of code.

Test-Driven development is a process of developing and running automated tests before the actual development of the application. TDD is sometimes called Test First Development.

We write the Test first and the Test acts as the specification. The specification is not on a piece of paper, it's actual code and we can run it and verify that we have achieved our goal.

The main is to write the test first and THEN write your production code. You do it often iteratively.

"You write the test so that you can then write production code. You don't write the test to test your code."

The Sequence of Steps;

• Read the requirements and Add Test cases,

• Run Test that will fail immediately

• Write the necessary code to pass the test as quickly as possible

• Run Test again

• Refactor Code

• Repeat

How to perform TDD Test?

• Add Test

• Execute Test

• Write your Code

• Repeat

Behaviour Driven Development; is an Agile software development methodology in which an application is documented and designed around the behaviour a user expects to experience when interacting with it. The BDD is written in plain English.

Example of a BDD Test;

Feature: Login functionality

As a customer

To use the application

I want to log in with email and password

Scenario: Logging in with invalid credentials

Given I am at the Account/Login Page

When I fill the account email textbox with the value "incorrect@mail.com"

And fill the password textbox with the value "incorrectpassword"

And click the login button

Then a text "Can't login! Wrong email or password." Should appear in the validation errors region.

Scenario: Logging in with valid credentials

Given I am at the Account/Login Page

When I fill the account email textbox with the value "myname@mymail.com"

And fill the password textbox with the value "mypassword"

And click the login button

Then I should be on the home page

Difference between TDD and BDD

• In TDD Test cases are written by developers in a programming language

, while in BDD the Test cases are written by Stakeholders(also users) in plain English

• The TDD is written to test each unit (module) of the code

, while in BDD we test end-to-end expectations from the Software.

• The TDD is suited for Unit Testing while the BDD is suitable for Acceptance Testing.