Learn about XHR Testing in Cypress

Tutorial 11​​ – XHR Testing​​ Introduction​​ in Cypress

What you will Learn :

  • What is XHR Request?

  • XHR testing with cypress

  • When to perform XHR testing?

  • Understand mocking and spying

  • Understand cy.server() command​​ 

  • Understand cy.route() command​​ for GET request

  • Understand cy.route() command for POST request

What is XHR​​ Request

XHR stands​​ for XMLHttpRequest and it is a javascript​​ API​​ that is used for communication between the client and the server.​​ Not only XML, this API can also be used​​ to request​​ JSON/HTML​​ data from web server.

XHR is used as part of the AJAX (Asynchronous Javascript and XML) technique. AJAX utilizes XHR to load data asynchronously from the server in the background without disturbing the behavior of​​ the web page. It is used in most​​ of the dynamic websites that you see today.

Most of the ecommerce websites​​ use​​ AJAX technique when searching for products and while showing the results. XHR is constantly being used as we type in the search box to show the​​ auto-suggestions. XHR is also used to load more results when we scroll to the bottom of the search results pages.

XHR testing with cypress

Cypress provides direct access to XHR methods and hence​​ we can make assertions about the​​ properties​​ (example, if the ‘status’ property equals 200).​​ So cypress can be used for clicking a button on a webpage & simultaneously it can make API calls.​​ 

If you want to perform API testing using Selenium, you have to integrate it with 3rd​​ party jars (example Rest Assured APIs). However in cypress, there is no need​​ to​​ integrate any 3rd​​ party to perform API testing.

When to perform XHR testing?

  • When you want to perform basic API testing using request() method

  • When you want to mock network responses

  • When you want to listen​​ to network Request/Responses​​ using route() method

Understand mocking and spying

You will understand mocking when we do practical examples​​ later. As of now, just try to understand the concept.

To mock​​ an application​​ means to​​ mock a backend request.​​ To mock a backend, all you have to do is to use the cypress server command​​ cy.server().​​ Once you​​ do​​ that,​​ you have a mock server​​ ready.​​ 

Once you have the mock server ready, you can start defining routes​​ that you want to spy on. In the below snapshot, we are going to spy on the ‘comments’ route when there is a GET request to it​​ (in the above figure, we are spying on the ‘todos’ route)

The​​ .as(‘getComment’) command allows us to label this route as an alias that we can refer again when required. Once we have mocked this route at the backend, we can go ahead and visit the route of my application​​ using cy.visit command

We can now use cypress wait command​​ to​​ wait on ‘getComment’ route

Now we can make assertions​​ (using ‘should’ as seen below)​​ on the DOM or on the body of the request

Below is syping again, its just that this time we are spying using POST request​​ 

Understand cy.server() command​​ 

The first thing, in order to work with HTTP requests is: we have to setup a server.​​ cy.server() command​​ initializes network related​​ behaviour.​​ 

So, whatever commands you​​ call​​ after cy.server() command,​​ cypress​​ will understand them as network​​ related​​ commands.​​ 

Look the url ​​​​ https://example.cypress.io/commands/network-requests


Understand cy.route() command​​ for GET request

cy.route()​​ command​​ initiates listening​​ to network Requests/network​​ Responses​​ viz this command initiates​​ listening the GET/POST/PUT requests.​​ 

To understand this, launch​​ https://example.cypress.io/commands/network-requests

Press​​ F12​​ key.​​ 

This​​ would open​​ up the Network tab​​ as seen below.

Click XHR​​ as seen below​​ 

Click ‘Get Comment’ button​​ that you see in the figure​​ above (on the left hand side).​​ 

So basically,​​ internally, the applicaion is​​ firing a GET method and​​ an​​ XHR request​​ would be seen, see below​​ on the right hand side

Click this​​ XHR​​ request​​ that you see on the right hand side​​ in above figure.

See the below figure.

In the ‘Headers’ section, you would see the Request URL (this is the api call that was made when​​ we had clicked the ‘Get Comment’ button).​​ 

In the ‘Headers’ section, you would also see the​​ Request Method (GET), Status code (200)​​ etc.

Go the to ‘Response’ tab now, see below

‘Response’​​ section shows the response that we get from the server, as seen above.​​ 

Notice that​​ the comment​​ can be seen​​ in the “body”

This is same comment that we get when we click ‘Get Comment’button, see below​​ 

Now let us try to understand the highlighted section​​ in the figure​​ below

The​​ cy.route() command will keep continously listening if any​​ GET​​ method is fired and as soon as the ‘Get Comment’ is​​ clicked, the response gets saved in the ‘getComment’ variable​​ 

Note that the css selctor for ‘Get Comment’ button is​​ .network-btn

The​​ request​​ url in the cy.route command is​​ ‘comments/*’

The star​​ in the request url comments/*​​ represents​​ any​​ comment​​ that is present in database.​​ You don’t have to mention the complete url here (since cypress understands this example)


Let us now understand cy.wait

In the cy.wait statement, we are simply reading the data from​​ ‘getComment’​​ variable and checking if the status equals 200. If the​​ status equals 200. it means that we have got the most latest comment from the server.

Let us clear the requests by clicking​​ ​​ clear

Understand cy.route() command for POST request

See below

Let us now click ‘Post Comment’​​ to post a new comment​​ in the database.

Now​​ see this POST​​ request in XHR​​ (see above).​​ The​​ status code as 201.​​ 

The status code ‘201 Created’ means that the request has been fulfilled and resulted in a new resource being created​​ in the database.

Also notice that we see the text ‘POST successful’ below the ‘Post Comment’ button

On the similar lines we can explain​​ that​​ cy.route()​​ is now listening to any POST request being made.​​ The response​​ is saved​​ to​​ ‘postComment’​​ variable

Note​​ 1:​​ The css selector for ‘Post Comment’ button is .network-post
Note 2:​​ The POST​​ request url is /comments without any star since we are posting the comments.

Let​​ us​​ now​​ understand​​ the second half of the​​ section

In the above section, we are reading​​ the data in @postComment​​ response​​ and​​ are​​ validating​​ various properties like​​ whether​​ requestBody includes ‘email’

….whether requestHeaders has property​​ content-type​​ and so on…

Thank you for reading!

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