JSDom does not mock window.MutationObserver.

Created by: deskoh

Is this a bug report?

Yes.

Did you try recovering your dependencies?

Yes.

Which terms did you search for in User Guide?

jsdom testing

Environment

Environment Info:

  System:
    OS: Windows 10
    CPU: x64 Intel(R) Xeon(R) CPU E3-1270 v6 @ 3.80GHz
  Binaries:
    npm: 6.4.1 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Edge: 44.17763.1.0
    Internet Explorer: 11.0.17763.1
  npmPackages:
    react: ^16.8.4 => 16.8.4
    react-dom: ^16.8.4 => 16.8.4
    react-scripts: 2.1.8 => 2.1.8
  npmGlobalPackages:
    create-react-app: Not Found

Steps to Reproduce

create-react-app jsdom-test
Add expect(window.MutationObserver).not.toBeUndefined(); to generated App.test.js.
Run npm run test.

Expected Behavior

npm run test should pass as window.MutationObserver should be defined by jsdom as tested using the following code:

// Mock DOM (https://airbnb.io/enzyme/docs/guides/jsdom.html)
const { JSDOM } = require('jsdom');
const jsdom = new JSDOM('<!doctype html><html><body></body></html>');
const { window } = jsdom;

const assert = require('assert');

assert(window.MutationObserver);

Actual Behavior

Test fails as window.MutationObserver is undefined.

  ● test MutationObserver

    expect(received).not.toBeUndefined()

    Received: undefined