with-dom-overwrites is a utility for easily stubbing / overwriting properties of the jsdom instance (at any nesting level) in jest tests. In other words, it allows for the ability to do this:

import withDomOverwrites from 'with-dom-overwrites'

describe('some document context', () => {
  it('should work', () => {
    withDomOverwrites({
      overwrites: {
        'window.top': {},
        'window.custom.prop': 'custom prop',
        'document.referrer': 'foo',
        'document.location.href': 'https://www.google.com',
        'document.documentElement.outerHTML': `
          <html data-foo="foo..">
            <body>
              <h1>Hello World</h1>
            </body>
          </html>
        `,
      },
      run: () => {
        expect(window.top).toEqual({})
        expect(window.custom.prop).toBe('custom prop')
        expect(document.referrer).toBe('foo')
        expect(document.location.href).toBe('https://www.google.com')
        expect(document.documentElement.getAttribute('data-foo')).toBe('foo..')
      }
    })
  })
})

Instead of having to do this:

import jsdom from 'jsdom';

describe('some scenario that happens in the browser', () => {
  it('should work', () => {
    const url = 'https://www.google.com'
    const windowTop = {}
    const referrer = 'foo'
    const html = `
      <html data-foo="foo..">
        <body>
          <h1>Hello World</h1>
        </body>
      </html>
    `
    const dom = new jsdom.JSDOM(html);
    const originalDocument = global.document;

    Object.defineProperty(global, 'window', {
      value: dom.window,
      writable: true
    });

    Object.defineProperty(global, 'document', {
      value: dom.window.document,
      writable: true
    });

    Object.defineProperty(window.document, 'referrer', {
      value: referrer,
      writable: true
    });    

    window.custom = { prop: 'custom prop' }
    
    dom.reconfigure({ url, windowTop });
 
    expect(window.top).toBe(windowTop)
    expect(window.custom.prop).toBe('custom prop)
    expect(document.referrer).toBe(referrer)
    expect(document.location.href).toBe(url)
    expect(document.documentElement.getAttribute('data-foo')).toBe('foo..')

    global.document = originalDocument;
  })
})

Installation

npm install with-dom-overwrites --save-dev

Motivation

Though it is easy to access the jsdom window / document object within a jest test, it's not always easy to manipulate them. For instance, trying to set the document URL by supplying a value to the document.location.href property will not work. Rather, to change the URL, one will have to use the jsdom.reconfigure method, which requires a custom jsdom environment in order to be used within a jest test. The same goes for setting the window.top property, and there are one or two other scenarios that require a custom jsdom environment. This is not ideal as not only is it a bit cumbersome to setup each time, all the steps required make it something that is easily forgotten. But this is not the only issue. Even with the things that can be changed directly on the global window object, changing them is not always straight forward as a lot of things require Object.defineProperty to be changed, which does not lead to the most concise code.

with-dom-overwrites aims to provide a single utility withDomOverwrites({...}) function that can be used to easily and uniformly overwrite values on the jsdom instance at any nesting level, while ensuring that the original jsdom instance is restored afterwards.

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Last updated on 17 May 2019

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Install

with-dom-overwrites