Mocking `document` in jest

Question

I'm trying to write tests for my web components projects in jest. I already use babel with es2015 preset. I'm facing an issue while loading the js file. I have followed a piece of code where document object has a currentScript object. But in test context it is null. So I was thinking of mocking same. But jest.fn() is not really help in same. How can I handle this issue?

Piece of code where jest is failing.

var currentScriptElement = document._currentScript || document.currentScript;
var importDoc = currentScriptElement.ownerDocument;

Test case I have written. component.test.js

import * as Component from './sample-component.js';

describe('component test', function() {
  it('check instance', function() {
    console.log(Component);
    expect(Component).toBeDefined();
  });
});

Following is the error thrown by jest

Test suite failed to run

    TypeError: Cannot read property 'ownerDocument' of null

      at src/components/sample-component/sample-component.js:4:39

Update: As per suggestion from Andreas Köberle, I have added some global vars and tried to mock like following

__DEV__.document.currentScript = document._currentScript = {
  ownerDocument: ''
};
__DEV__.window = {
  document: __DEV__.document
}
__DEV__.document.registerElement = jest.fn();

import * as Component from './arc-sample-component.js';

describe('component test', function() {
  it('check instance', function() {
    console.log(Component);
    expect(Component).toBeDefined();
  });
});

But no luck

Update: I have tried above code without __dev__. Also by setting document as global.

Answer 1

Similar to what others have said, but instead of trying to mock the DOM yourself, just use JSDOM:

mocks/client.js

import { JSDOM } from "jsdom"
const dom = new JSDOM()
global.document = dom.window.document
global.window = dom.window

Then in your jest config:

    "setupFiles": [
      "./__mocks__/client.js"
    ],