🕚React Testing Library (events)

Firing Events | Testing Library

Excerpt

Note

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Note

Most projects have a few use cases for fireEvent, but the majority of the time you should probably use [@testing-library/user-event](https: //testing-library.com/docs/ecosystem-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](https: //github.com/testing-library/dom-testing-library/blob/master/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', charCode: 13})fireEvent.keyDown(domNode, {key: 'A', code: 'KeyA'})

You can find out which key code to use at [https: //keycode.info/](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 inputfireEvent(  input,  createEvent('input', input, {    target: {files: inputFiles},    ...init,  }),)

Using Jest Function Mocks

[Jest's Mock functions](https: //jestjs.io/docs/en/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)})