Mocking animation completion callback in jest

user_2131598 0
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I'm trying to write a unit test with Jest for a Reactcomponent that utilises Transition from react-transition-group. I need to mock the Transition so my tests don't have to wait for the animation to complete. However, in addition to 'skipping' the animation, I need the onExited callback to fire on my mocked Transition component.

Here's how my Component.js is using Transition:

...
return (
  <Transition
    timeout={1500}
    in={this.state.show}
    onExited={handleExited}>
    {status =>
      <button onClick={this.setState({show: false}) className={`component-${status}`}>button</button>
    }
  </Transition>
)

And here's my Component.test.js:

import React from 'react'
import {render, fireEvent} from 'react-testing-library'

import Component from '../Component'

test('check', () => {
  const handleCompletion = jest.fn()
  const {getByText} = render(
    <Component
      onButtonClick={handleCompletion}
    />
  )
  const button = getByText('button')
  fireEvent.click(button)
  expect(handleCompletion).toHaveBeenCalledTimes(1)
})

The idea is that once a button is clicked, the component animates and then, on completion, fires a callback.

How do I mock the Transition correctly so it skips the animation but still fires the onExited callback?

react-transition-group jestjs reactjs mocking
1 Answers

You can mock modules with jest.mock like so:

jest.mock('react-transition-group', () => ({
    Transition: (props) => {
        props.onExited() // you can call it asynchronously too, if you wrap it in a timeout
        return <div>
            {props.in ? props.children() : null}
        </div>
    }
}))
user_72284270
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