Firing Events

Note
Most projects have a few use cases for fireEvent, but the majority of the time you should probably use @testing-library/user-event.

`fireEvent`

fireEvent(node: HTMLElement, event: Event)

Fire DOM events.

// <button>Submit</button>
fireEvent(
  getByText(container, 'Submit'),
  new MouseEvent('click', {
    bubbles: true,
    cancelable: true,
  })
)

`fireEvent[eventName]`

fireEvent[eventName](node: HTMLElement, eventProperties: Object)

Convenience methods for firing DOM events. Check out src/event-map.js for a full list as well as default eventProperties.

target: When an event is dispatched on an element, the event has the subjected element on a property called target. As a convenience, if you provide a target property in the eventProperties (second argument), then those properties will be assigned to the node which is receiving the event.

This is particularly useful for a change event:

fireEvent.change(getByLabelText(/username/i), { target: { value: 'a' } })

// note: attempting to manually set the files property of an HTMLInputElement
// results in an error as the files property is read-only.
// this feature works around that by using Object.defineProperty.
fireEvent.change(getByLabelText(/picture/i), {
  target: {
    files: [new File(['(⌐□_□)'], 'chucknorris.png', { type: 'image/png' })],
  },
})

// Note: The 'value' attribute must use ISO 8601 format when firing a
// change event on an input of type "date". Otherwise the element will not
// reflect the changed value.

// Invalid:
fireEvent.change(input, { target: { value: '24/05/2020' } })

// Valid:
fireEvent.change(input, { target: { value: '2020-05-24' } })

dataTransfer: Drag events have a dataTransfer property that contains data transferred during the operation. As a convenience, if you provide a dataTransfer property in the eventProperties (second argument), then those properties will be added to the event.

This should predominantly be used for testing drag and drop interactions.

fireEvent.drop(getByLabelText(/drop files here/i), {
  dataTransfer: {
    files: [new File(['(⌐□_□)'], 'chucknorris.png', { type: 'image/png' })],
  },
})

Keyboard events: There are three event types related to keyboard input - keyPress, keyDown, and keyUp. When firing these you need to reference an element in the DOM and the key you want to fire.

fireEvent.keyDown(domNode, { key: 'Enter', code: 'Enter' })

fireEvent.keyDown(domNode, { key: 'A', code: 'KeyA' })

You can find out which key code to use at https://keycode.info/.

`createEvent[eventName]`

createEvent[eventName](node: HTMLElement, eventProperties: Object)

Convenience methods for creating DOM events that can then be fired by fireEvent, allowing you to have a reference to the event created: this might be useful if you need to access event properties that cannot be initiated programmatically (such as timeStamp).

const myEvent = createEvent.click(node, { button: 2 })
fireEvent(node, myEvent)
// myEvent.timeStamp can be accessed just like any other properties from myEvent
// note: The access to the events created by `createEvent` is based on the native event API,
// Therefore, native properties of HTMLEvent object (e.g. `timeStamp`, `cancelable`, `type`) should be set using Object.defineProperty
// For more info see: https://developer.mozilla.org/en-US/docs/Web/API/Event

You can also create generic events:

// simulate the 'input' event on a file input
fireEvent(
  input,
  createEvent('input', input, {
    target: { files: inputFiles },
    ...init,
  })
)

Using Jest Function Mocks

Jest's Mock functions can be used to test that a callback passed to the function was called, or what it was called when the event that should trigger the callback function does trigger the bound callback.

React

import { render, screen, fireEvent } from '@testing-library/react'

const Button = ({ onClick, children }) => (
  <button onClick={onClick}>{children}</button>
)

test('calls onClick prop when clicked', () => {
  const handleClick = jest.fn()
  render(<Button onClick={handleClick}>Click Me</Button>)
  fireEvent.click(screen.getByText(/click me/i))
  expect(handleClick).toHaveBeenCalledTimes(1)
})

fireEvent#

fireEvent[eventName]#

createEvent[eventName]#

Using Jest Function Mocks#

`fireEvent`

`fireEvent[eventName]`

`createEvent[eventName]`

Using Jest Function Mocks