invoke

Invoke a function on the previously yielded subject.

Syntax

.invoke(functionName)
.invoke(options, functionName)
.invoke(functionName, args...)
.invoke(options, functionName, args...)

Usage

Correct Usage

cy.wrap({ animate: fn }).invoke('animate') // Invoke the 'animate' function
cy.get('.modal').invoke('show') // Invoke the jQuery 'show' function

Incorrect Usage

cy.invoke('convert') // Errors, cannot be chained off 'cy'
cy.wrap({ name: 'Jane' }).invoke('name') // Errors, 'name' is not a function

Arguments

functionName (String, Number)

Name of function to be invoked.

options (Object)

Pass in an options object to change the default behavior of .invoke().

args...

Additional arguments to be given to the function call. There is no limit to the number of arguments.

Examples

Function

Assert on a function's return value

const fn = () => {
  return 'bar'
}

cy.wrap({ foo: fn }).invoke('foo').should('eq', 'bar') // true

Use .invoke() to test HTML content

Properties that are functions are invoked

In the example below, we use .invoke() to force a hidden div to be 'display: block' so we can interact with its children elements.

cy.get('div.container')
  .should('be.hidden') // element is hidden
  .invoke('show') // call jquery method 'show' on the '.container'
  .should('be.visible') // element is visible now
  .find('input') // drill down into a child "input" element
  .type('Cypress is great') // and type text

Use .invoke('show') and .invoke('trigger')

Function with Arguments

Send specific arguments to the function

const fn = (a, b, c) => {
  return a + b + c
}

cy.wrap({ sum: fn })
  .invoke('sum', 2, 4, 6)
  .should('be.gt', 10) // true
  .and('be.lt', 20) // true

Use cy.invoke('removeAttr', 'target') to get around new tab

Arguments are automatically forwarded to the function

cy.get('img').invoke('attr', 'src').should('include', 'myLogo')

Arrays

In the above examples, the subject was an object, but cy.invoke also works on arrays and allows using numerical index to pick a function to run.

const reverse = (s) => Cypress._.reverse(s)
const double = (n) => n * n

// picks function with index 1 and calls it with argument 4
cy.wrap([reverse, double]).invoke(1, 4).should('eq', 16)

Invoking an async function

In this example we have a little text input field and we invoke an async action which will disable this input field. .invoke() will then wait until the Promise resolves and only then will continue executing to check if it really has been disabled.

Our input field

<input type="text" name="text" data-cy="my-text-input" />

The Cypress test with cy.invoke() awaiting the promise:

function disableElementAsync(element) {
  return new Promise((resolve) => {
    setTimeout(() => {
      element.disabled = true
      resolve()
    }, 3000)
  })
}

cy.get('[data-cy=my-text-input]').then((textElements) => {
  cy.wrap({ disableElementAsync }).invoke(
    'disableElementAsync',
    textElements[0]
  )
})

// log message appears after 3 seconds
cy.log('after invoke')

// assert UI
cy.get('[data-cy=my-text-input]').should('be.disabled')

jQuery method

If the parent command yields a jQuery element, we can invoke a jQuery method, like attr, text, or val. To confirm the element's id attribute for example:

<div id="code-snippet">The code example</div>

cy.contains('The code example')
  .invoke('attr', 'id')
  .should('equal', 'code-snippet')

Tip: Cypress has a built-in Chai-jQuery assertion to confirm the attribute. The above example can be written simply as:

cy.contains('The code example').should('have.attr', 'id', 'code-snippet')

Notes

Third Party Plugins

Using a Kendo DropDown

If you are using jQuery then the jQuery wrapped elements will automatically have your 3rd party plugins available to be called.

cy.get('input')
  .invoke('getKendoDropDownList')
  .then((dropDownList) => {
    // yields the return of $input.getKendoDropDownList()
    return dropDownList.select('apples')
  })

We can rewrite the previous example in a more terse way and add an assertion.

cy.get('input')
  .invoke('getKendoDropDownList')
  .invoke('select', 'apples')
  .invoke('val')
  .should('match', /apples/)

Retries

.invoke() automatically retries invoking the specified method until the returned value satisfies the attached assertions. The example below passes after 1 second.

let message = 'hello'
const english = {
  greeting() {
    return message
  },
}

setTimeout(() => {
  message = 'bye'
}, 1000)

// initially the english.greeting() returns "hello" failing the assertion.
// .invoke('greeting') tries again and again until after 1 second
// the returned message becomes "bye" and the assertion passes
cy.wrap(english).invoke('greeting').should('equal', 'bye')

Rules

Requirements

• .invoke() requires being chained off a previous command.

Assertions

• .invoke() will wait for the function to exist on the subject before running.
• .invoke() will wait for the promise to resolve if the invoked function returns a promise.
• .invoke() will automatically retry until all chained assertions have passed

Timeouts

• .invoke() can time out waiting for assertions you've added to pass.
• .invoke() can time out waiting for a promise you've returned to resolve.

Command Log

Invoke jQuery show method on element

cy.get('.connectors-div')
  .should('be.hidden')
  .invoke('show')
  .should('be.visible')

The commands above will display in the Command Log as:

When clicking on invoke within the command log, the console outputs the following:

History

See also

• .its()
• .then()
• cy.wrap()