How do you use Jest to test img.onerror

Question

I\'ve created a React component that loads an image and determines if the image loaded successfully or not.

import React from \'react\';
import PropTypes fro         


        

Answer 1

You could mock document.createElement:

 it('should call any passed in onError after an image load error', () => {
    const img = {}
    global.document.createElement = (type) => type === 'img' ? img : null
    const onError = jest.fn();
    mount();
    img.onload()
    expect(onError).toHaveBeenCalled();
  });