Introducing Cypress with Cucumber BDD

Tutorial 13​​ ​​ Introducing​​ Cypress​​ with Cucumber​​ BDD​​ 

What you will Learn :

  • What is​​ BDD (Business driven development)​​ ?

  • Gherkin syntax

  • E2E shopping cart Gherkin syntax

  • Scenario​​ keyword

  • Feature keyword

  • Linking Gherkin with cypress

  • Cucumber

  • Step Definition

  • References

What is​​ BDD​​ and Gherkin syntax

Let us first understand what is BDD. Go to the website​​ https://cucumber.io/​​ 

Look at above​​ test case.​​ We have​​ described​​ our test case in​​ the​​ form of​​ a ‘behaviour’.​​ 

So our automation test case will check whether ‘Alice will be full if she eats 3 cucumbers’. ​​​​ 

However, look at the below test case that was built​​ using pure cypress​​ syntax. To a client/end-user, the syntax​​ looks to be slighlty technical​​ and is not so easy to understand.

So by looking at above, it is difficult for the client to understand what exactly you have automated, what test case feature has been automated. They can only guess​​ what this​​ test case​​ might be doing.​​ So the business scenarios are missing in above​​ script.​​ So we cannot say for sure what the above test case exactly does.

Instead, our test case can be described in this behaviour driven style (see below).​​ 

The above syntax is called as ‘Gherkin’ syntax and our client can easily understand it. The syntax closely matches with the English​​ language​​ (having ‘Given’, ‘When’, Then’ etc keywords).​​ Most lines in a Gherkin syntax start with one of the keywords (Given, When etc).

So you can understand the test case syntax as below:

Given​​ explains what you have
When​​ you perform some action
And​​ you perform additional action
Then​​ what is the result or outcome of that action

Below is another example of​​ a test case in​​ Gherkin syntax.

Scenario: All​​ shopping​​ done

 ​​​​ Given​​ I am out shopping

 ​​​​ And​​ I have eggs

 ​​​​ And​​ I have milk

 ​​​​ And​​ I have butter

 ​​​​ When​​ I check my​​ shopping​​ list

 ​​​​ Then​​ I​​ should not have​​ anything​​ left

So you can describe your test scenario​​ using Gherkin syntax and you can link these lines with actual cypress code.

E2E shopping cart Gherkin syntax

In tutorial 7, we have already seen how to automate an end to end test case using cypress. Below were the steps that we automated:

Let us try to convert​​ above​​ steps​​ into​​ Gherkin syntax. So, below is the business representation in BDD/cucumber world​​ which is self-explanatory.​​ Recall that ‘And’ keyword is used to concatenate additional actions.​​ 

Scenario: E2E automation

 ​​​​ Given​​ I launch an e-commerce website

 ​​​​ When​​ I enter ‘Lenovo IdeaCentre 600 All-in-One PC’ in search field

 ​​​​ And​​ I search the item

 ​​​​ And​​ I​​ add item​​ to shopping cart

 ​​​​ And​​ I​​ go to shopping cart

 ​​​​ And​​ I enter 2 in quantity field

 ​​​​ And​​ I update my shopping cart

 ​​​​ Then​​ 'Total' amount should​​ be​​ $1000

Scenario​​ keyword

As you must have noticed in above test cases, in addition to other keywords, we also used ‘Scenario’ keyword.​​ A ‘Scenario’ describes intended behaviour of the test case. In other words, a ‘Scenario’ describes​​ what,​​ not​​ how.

Consider below test case. The ‘Scenario’ is describing the​​ what​​ viz​​ what the free subscribers will see. It does not describe​​ how the free subscribers will see only free articles.​​ 

Feature keyword

‘Feature’ represents a Test Suite.​​ A test suite can have multiple test cases. Each scenario represents​​ one test case. So if you consider below example, we have a ‘Feature’ that contains 2 test cases or 2 scenarios.

Linking Gherkin with cypress

Let us look at below test case again.​​ We will​​ ultimately​​ be linking all our Gherkin syntax with cypress code, as shown below.​​ 

Scenario: E2E automation

 ​​​​ Given​​ I launch an e-commerce website​​ linked to cy.visit('https://demo.nopcommerce.com/')

 ​​​​ When​​ I enter ‘Lenovo IdeaCentre 600 All-in-One PC’ in search field​​ linked to cy.get('.search-box-text').type('Lenovo IdeaCentre 600 All-in-One PC')

 ​​​​ And​​ I search the item​​ linked to​​ 
cy.get('.button-1[type=submit]').click()

 ​​​​ And​​ I add item to shopping cart​​ linked to​​ 
cy.get('.product-box-add-to-cart-button').click()

 ​​​​ And​​ I go to shopping cart​​ linked to​​ 
cy.get('.cart-label').click()

 ​​​​ And​​ I enter 2 in quantity field​​ linked to​​ 
​​ cy.get('.qty-input').clear().type('2')

 ​​​​ And​​ I update my shopping cart​​ linked to​​ 
​​ cy.get("[value='Update shopping cart']").click()

 ​​​​ Then​​ 'Total' amount should be $1000​​ linked to cy.get('.product-subtotal').contains('$1,000.00')

However, we will not share the cypress code with end user, we will only share the BDD (behaviour​​ driven development) Gherkin syntax.​​ 

Cucumber

As we have seen above,​​ we​​ describe the desired behaviour in a​​ test case and based upon this behaviour, we​​ drive​​ our development.​​ By development, we mean writing the actual cypress code​​ and linking it to behaviour. That’s the reason we call it as ‘Behaviour Driven Development’

Cucumber is one of the tool​​ which supports this BDD framework.

Step Definition

Now, what is a step?​​ Each line of a scenario is a step. So basically, all the below are steps.​​ To define these steps would mean to write the actual cypress code.​​ 

In ‘Behaviour Driven Development’, we write our cypress code inside ‘Step Definition’ file.​​ The link-up depends upon the programming language you are using. Different programming languages have different syntaxes to link.

We know that cypress is built on java script.​​ Go to the link​​ https://github.com/cucumber/cucumber-js​​ 

When you scroll down, you would see a link ‘Step Definitions’

Click ‘Step Definitions’ link. You would see an example of Gherkin and the corresponding JS syntax, see below

​​ 

 

We will look at the code details starting from next tutorial onwards.

References

You can refer the link​​ https://cucumber.io/docs/gherkin/reference/​​ to​​ read​​ more about Gherkin syntax

You can refer the link​​ https://cucumber.io/docs/cucumber/step-definitions/​​ for understanding ‘Step Definition’ in detail

Thank you​​ for reading!

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