What is BDD and How to implement using Cucumber ?

Cucumber

• A testing framework which supports BDD.
• Define your application behavior in plain english language.
• Grammer is defined by Gherkin langauge

Challenges with TDD 
Normally, developers develops features but write test code later. Due to need of release, he does quick but inefficient testing.  
Test-cases focus on the functionality of its integration.


BDD

• Takes care of workflow in place of functionality.
• Application is designed by describing its behavior for outside observer.
• Behavior is written in readable and understandable language.
• Behavior is defined in Given-When-Then steps.

Gherkin
Business-readable domain specific language
Understandable for BA, testers and customer perspective
Allows creating precise acceptance criteria

Example
Scenario: Eat 5 out of 12 

Given there are 12 cucumbers 

When I eat 5 cucumbers

Then I should have 7 cucumbers 




Feature file consists following components :  
1. Feature: Description of the current test script which has to be executed.
2. Scenario: Description of the steps and expected outcome for a particular test case.
3. Scenario Outline: Same scenario can be executed for multiple sets of data using scenario outline. The data is provided by a tabular structure separated by |
4. Given: Context of the text to be executed. By using data tables "Given", step can also be parameterized.
5. When: Test action that has to performed
6. Then: Expected outcome of the test can be represented by "Then"



STEP DEFINITION
It maps the test case steps in the feature files (introduced by Given/When/Then) to code, which executes and checks the outcomes from the system under test.