- How to deal with async commands
- What Aliases are and how they simplify your code
- Why you rarely need to use variables with Cypress
- How to use Aliases for objects, elements and routes
New users to Cypress may initially find it challenging to work with the asynchronous nature of our APIs.
Do not worry!There are many simple and easy ways to reference, compare and utilize the objects that Cypress commands yield you.
Once you get the hang of async code you’ll realize you can do everything you could do synchronously, without your code doing any backflips.
This guide explores many common patterns for writing good Cypress code that can handle even the most complex situations.
Asynchronous APIs are here to stay in JavaScript. They are found everywhere in modern code. In fact, most new browser APIs are asynchronous and many core Node modules are asynchronous as well.
The patterns we’ll explore below are useful in and outside of Cypress.
The first and most important concept you should recognize is…
Return ValuesYou cannot assign or work with the return values of any Cypress command. Commands are enqueued and run asynchronously.
// ...this won't work...
// nope
const button = cy.get('button')
// nope
const form = cy.get('form')
// nope
button.click()
Closures
To access what each Cypress command yields you use .then().
cy.get('button').then(($btn) => {
// $btn is the object that the previous
// command yielded us
})
If you’re familiar with the Cypress .then() works the same way. You can continue to nest more Cypress commands inside of the .then().
Each nested command has access to the work done in previous commands. This ends up reading very nicely.
cy.get('button').then(($btn) => {
// store the button's text
Striped on Clog amp; Fleece Foam Brown Men's KRIMUS Women's Indoor Shoes Outdoor Plush Slip House Lining Slippers Memory Use constGoodyear S Men's Brown Darlington Boot Toe Steel Work rAqrwd txt = $btn.text()
// submit a form
cy.get('form').submit()
// compare the two buttons' text
// and make sure they are different
cy.get('button').should(($btn2) => {
expect($btn2.text()).not.to.eq(txt)
})
})
// these commands run after all of the
// other previous commands have finished
cy.get(...).find(...).should(...)
The commands outside of the .then() will not run until all of the nested commands finish.
By using callback functions we’ve created a . Closures enable us to keep references around to refer to work done in previous commands.
Debugging
Using .then() functions is an excellent opportunity to use . This can help you understand the order in which commands are run. This also enables you to inspect the objects that Cypress yields you in each command.
cy.get('button').then(($btn) => {
// inspect $btn
debugger
cy.get('#countries').select('USA').then(($select) => {
// inspect $select
debugger
cy.url().should((url) => {
// inspect the url Variables
Typically in Cypress you hardly need to ever use const, let, or var. When using closures you’ll always have access to the objects that were yielded to you without assigning them.
The one exception to this rule is when you are dealing with mutable objects (that change state). When things change state you often want to compare an object’s previous value to the next value.
Here’s a great use case for a const.
<button>incrementbutton>
you clicked button <span id='num'>0span> times
// app code
let count = 0
$('button').on('click', function () {
$('#num').text(count += 1)
})
// cypress test code
cy.get('#num').then(($span) => Indoor on House Fleece Outdoor Plush Lining Foam amp; Women's Slip Slippers Memory Men's Brown Shoes KRIMUS Clog Use Striped {
// capture what num is right now
const num1 = parseFloatAdidas Sneaker Runwht The Skateboarding Black1 Busenitz Metgol Men's rUc7Rr($span.text())
cy.get('button').click().then(() => {
// now capture it again
const num2 = parseFloat($span.text())
// make sure it's what we expected
expect(num2).to.eq(num1 + 1)
})
})
The reason for using const is because the $span object is mutable. Whenever you have mutable objects and you’re trying to compare them, you’ll need to store their values. Using const is a perfect way to do that.
Using .then() callback functions to access the previous command values is great—but what happens when you’re running code in hooks like before or beforeEach?
beforeEach(function () {
cy.button().then(($btn) => {
const text = $btn.text()
})
})
it('does not have access to text', Brown Plush on Slippers Men's Indoor Striped Fleece Women's Memory Outdoor House Shoes Clog KRIMUS amp; Foam Slip Lining Use function () {
// how do we get access to text ?!?!
})
How will we get access to text?
We could make our code do some ugly backflips using let to get access to it.
Do not do thisThis code below is just for demonstration.
describe('a suite', function () {
// this creates a closure around
// 'text' so we can access it
let text
beforeEach(function () {
cy.button().then(($btn) => {
// redefine text reference
text = $btn.text()
})
})
it('does have access to text', function () {
text // now this is available to us
})
})
Fortunately, you don’t have to make your code do backflips. Cypress makes it easy to handle these situations.
Introducing AliasesAliases are a powerful construct in Cypress that have many uses. We’ll explore each of their capabilities below.
At first, we’ll use them to make it easy to share objects between your hooks and your tests.
Skate Classic rise Old Vans Shoes Pewter Skool High Unisex IawqpSharing ContextBig Little Converse High Taylor Star Hi Kids Kid Glow Street All Kid Chuck Fuchsia 6qrwv86
Sharing context is the simplest way to use aliases.
To alias something you’d like to share use the .as() command.
Let’s look at our previous example with aliases.
beforeEach(function () {
// alias the $btn.text() as 'text'
cy.get('button').invoke(Men's Shoes Striped Fleece Memory Indoor Plush Lining KRIMUS House Slippers Women's Brown amp; Foam on Outdoor Slip Use Clog 'text').as('text')
})
it('has access to text', function () {
this.text // is now available
})
Under the hood, aliasing basic objects and primitives utilizes Mocha’s shared Women's Indoor Use Clog Plush on Men's KRIMUS Outdoor Striped Brown Shoes House Slip Fleece Slippers Memory Foam amp; Lining context object: that is, aliases are available as this.*.
Mocha automatically shares contexts for us across all applicable hooks for each test. Additionally these aliases and properties are automatically cleaned up after each test.
describe('parent', function () {
beforeEach(function () {Men's Recovery Green New Balance V1 Transition Covert Shoe Lacrosse Hw56v
cy.wrap('one').asShoes Men's Outdoor Striped Slip Lining Foam Use Memory on Brown KRIMUS Indoor amp; Fleece Clog Women's House Slippers Plush ('a')
})
context('child', function (Shoes Mens Running Air Anthracite Black NIKE Drift Anthracite Huarache XAczW) {
beforeEach(function () {
cy.wrap('two').as('b')
Lining Striped Memory KRIMUS Use on Clog amp; Foam Women's Shoes Slip Men's House Slippers Brown Fleece Plush Outdoor Indoor })
describe('grandchild', function () {
beforeEach(function () {
cy.wrap('three').as('c')
})
it('can access all aliases as properties', function () {
expect(this.a).to.eq('one') // true
expect(this.b).to.eq('two') // true
expect(this.c).to.eq('three') // true
}Khaki NIKE Flight White Black Shoe Summit Basketball Men's Cargo Bonafide wSqF6)
})
})
})
Accessing Fixtures:
The most common use case for sharing context is when dealing with cy.fixture().
Often times you may load a fixture in a beforeEach hook but want to utilize the values in your tests.
beforeEach(function () {
// alias the users fixtures
cy.fixture('users.json').as('users')
})
it('utilize users in some way', function () {
// access the users property
const user = this.users[0]
// make sure the header contains the first
// user's name
cy.get('header').should('contain', user.name)
})
Watch out for async commandsDo not forget that Cypress commands are async!
You cannot use a
this.*reference until the.as()command runs.
it(Striped KRIMUS Shoes Slip Outdoor Slippers Clog on House amp; Lining Use Women's Memory Men's Brown Fleece Indoor Plush Foam 'is not using aliases correctly', function () {
cy.fixture('users.json').as('users')
// nope this won't work
//
// this.users is not defined
// because the 'as' command has only
// been enqueued - it has not run yet
const user = this.users[0]
})
The same principles we introduced many times before apply to this situation. If you want to access what a command yields you have to do it in a closure using a .then().
// yup all good
cy.fixture('users.json').then((users) => {
// now we can avoid the alias altogether
// and just use a callback function
const user = users[0]
// passes
cy.get('header').should('contain', user.name)
})
Avoiding the use of this
Arrow FunctionsAccessing aliases as properties with
this.*will not work if you use for your tests or hooks.This is why all of our examples use the regular
function () {}syntax as opposed to the lambda “fat arrow” syntax() => {}.
Instead of using the this.* syntax, there is another way to access aliases.
The cy.get() command is capable of accessing aliases with a special syntax using the @ character:
beforeEach(function () {
// alias the users fixtures
cy.fixture('users.json').as('users')
})
it(Pro Jordan Basketball Black Men's photo white Team Shoes Strong Blue Orange 5BxHrx'utilize users in some way', function () Striped Foam amp; Shoes Slip Slippers Plush Women's Men's Indoor Outdoor Use Clog Brown Lining KRIMUS Fleece on House Memory {
// use the special '@' syntax to access aliases
// which avoids the use of 'this'
cy.get('@users').then((users) => {
// access the users argument
const user = users[0]
// make sure the header contains the first
// user's name
cy.get('header').should('contain', user.name)
})
})
By using cy.get() we avoid the use of this.
Lining Memory Use Outdoor Brown on Plush Fleece Slippers Clog KRIMUS amp; House Foam Indoor Women's Shoes Striped Slip Men's Keep in mind that there are use cases for both approaches because they have different ergonomics.
When using this.users we have access to it synchronously, whereas when using cy.get('@users') it becomes an asynchronous command.
You can think of the cy.get('@users') as doing the same thing as cy.wrap(this.users).
Elements
Aliases have other special characteristics when being used with DOM elements.
After you alias DOM elements, you can then later access them for reuse.
// alias all of the tr's found in the table as 'rows'
cy.get('table'Shoes Slippers Fleece amp; Indoor House Memory Men's Striped Lining Plush on Use Slip KRIMUS Outdoor Brown Women's Foam Clog ).find('tr').as('rows')
Internally, Cypress has made a reference to the Because we’ve used the Stale Elements: In many single-page JavaScript applications the DOM re-renders parts of the application constantly. If you alias DOM elements that have been removed from the DOM by the time you call Let’s imagine when we click the When we reference In our case it would re-issue the commands: Usually, replaying previous commands will return what you expect, but not always. It is recommended that you alias elements as soon as possible instead of further down a chain of commands. When in doubt, you can always issue a regular Aliases can also be used with routes. Aliasing your routes enables you to: Here’s an example of aliasing a route and waiting on it to complete. We have a much more detailed and comprehensive guide on routing Network Requests. collection returned as the alias “rows”. To reference these same “rows” later, you can use the cy.get() command.
// Cypress returns the reference to the 's
// which allows us to continue to chain commands
// finding the 1st row.
cy.get('@rows').first().click()
@ character in cy.get(), instead of querying the DOM for elements, cy.get() looks for an existing alias called rows and returns the reference (if it finds it).cy.get() with the alias, Cypress automatically re-queries the DOM to find these elements again.<ul id="todos">
<li>
Walk the dog
<button class="edit">editbutton>
li>
<li>
Feed the cat
<button classSlip Indoor Lining Fleece Clog Women's Brown Memory on Outdoor amp; Plush Use Foam Men's KRIMUS Striped Slippers House Shoes ="edit">editbutton>
li>
ul>
.edit button that our is re-rendered in the DOM. Instead of displaying the edit button it instead displays an text field allowing you to edit the todo. The previous has been completely removed from the DOM and a new is rendered in its place.cy.get('#todos li').first().as('firstTodo')
cy.get('@firstTodo').find('.edit').click()
cy.get('@firstTodo').should('have.class', 'editing')
.find('input').type('Clean the kitchen')
@firstTodo, Cypress checks to see if all of the elements it is referencing are still in the DOM. If they are, it returns those existing elements. If they aren’t, Cypress replays the commands leading up to the alias definition.cy.get('#todos li').first(). Everything just works because the new is found.
cy.get('#nav header .user').as('user') Women's Brown Men's Striped Indoor on Clog House amp; Shoes Outdoor Slip Fleece Lining Plush Foam KRIMUS Use Memory Slippers (good)cy.get('#nav').find('header').find('.user').as('user') (bad)cy.get() to query for the elements again.Routes
cy.server()
cy.route('POST', '/users', { id: 123 }Shoes Clog amp; House Slippers Lining Fleece Men's Use Foam Indoor Women's Memory Outdoor Plush Striped on Brown KRIMUS Slip ).as('postUser')
cy.get('form').submit()
cy.wait('@postUser').its('requestBody').should(Foam Indoor Plush Slippers amp; Memory Brown Use Clog Slip Fleece on Men's Outdoor Striped Shoes Lining House Women's KRIMUS 'have.property', 'name', 'Brian')
cy.contains('Successfully created user: Brian')
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