CODEWITHSUNDEEP
javascriptmockingjestjs
danny
danny

Reputation: 3266

How can I mock the JavaScript 'window' object using Jest?

I need to test a function which opens a new tab in the browser

openStatementsReport(contactIds) {
  window.open(`a_url_${contactIds}`);
}

I would like to mock window's open function, so I can verify the correct URL is passed in to the open function.

Using Jest, I don't know how to mock window. I tried to set window.open with a mock function, but this way doesn't work. Below is the test case:

it('the correct URL is called', () => {
  window.open = jest.fn();
  statementService.openStatementsReport(111);
  expect(window.open).toBeCalled();
});

But it gives me the error

expect(jest.fn())[.not].toBeCalled()

jest.fn() value must be a mock function or spy.
    Received:
      function: [Function anonymous]

What should I do to the test case?

Upvotes: 249

Views: 385028

Answers (17)

Danny Pule
Danny Pule

Reputation: 1130

Date: July 2023

Jest version: 28.1.3

This version spys on window.open (via global.open) then restores window.open after all tests are completed.

const realOpen = global.open; // store real window.open

describe('Given [thing you are testing]', () => {
  beforeAll(() => {
    jest.spyOn(global, 'open'); // create spy in beforeAll hook
  });

  afterAll(() => {
    global.open = realOpen; // after all the tests are completed restore window.open in afterAll hook
  });

  it('the correct URL is called', () => {
    jest.clearAllMocks(); // clear all mocks before running statementService.openStatementsReport
    statementService.openStatementsReport(111);
    expect(global.open).toBeCalled();
  });
});

Upvotes: 0

Chris Perry
Chris Perry

Reputation: 7904

The window object in Jest is self-mocking

One of the things unaddressed in other answers is a comment by the OP:

Using Jest, I don't know how to mock the window.

The window object is already mocked and can be referenced out of the box.

From the documentation:

Jest ships with jsdom which simulates a DOM environment as if you were in the browser. This means that every DOM API that we call can be observed in the same way it would be observed in a browser!

Example:

describe('i am a window', () => {
    it('has a window object', () => {
      expect(window).toBeTruthy(); // test will pass
    });
});

Upvotes: 9

Poh Zi How
Poh Zi How

Reputation: 1569

We can also define it using global in setupTests:

// File 'setupTests.js'
global.open = jest.fn()

And call it using global in the actual test:

// File 'yourtest.test.js'
it('the correct URL is called', () => {
    statementService.openStatementsReport(111);
    expect(global.open).toBeCalled();
});

Upvotes: 17

Andreas Köberle
Andreas Köberle

Reputation: 111062

Instead of window, use global:

it('the correct URL is called', () => {
  global.open = jest.fn();
  statementService.openStatementsReport(111);
  expect(global.open).toBeCalled();
});

You could also try:

const open = jest.fn()
Object.defineProperty(window, 'open', open);

Upvotes: 135

MohammadReza Abbasi
MohammadReza Abbasi

Reputation: 500

You can test it:

describe('TableItem Components', () => {
    let open_url = ""
    const { open } = window;
    beforeAll(() => {
        delete window.open;
        window.open = (url) => { open_url = url };
    });
    afterAll(() => {
        window.open = open;
    });
    test('string type', async () => {
        wrapper.vm.openNewTab('http://example.com')
        expect(open_url).toBe('http://example.com')
    })
})

Upvotes: 1

Evgeniy Boytsov
Evgeniy Boytsov

Reputation: 314

Try simply:

let windowOpenSpy: jest.SpyInstance;
beforeEach(() => {
    windowOpenSpy = jest.spyOn(window, 'open');
});

it('should open window with dashboard url', () => {
    expect(windowOpenSpy).toBeCalledWith('your URL', '_blank');
});

Upvotes: 4

Giselle Rosa
Giselle Rosa

Reputation: 31

I tried a similar test, and it worked with me...

My code:

export const Blah = () => {
        const BLAH = 'https://www.google.com/'
        const handleBlah = () => {
            window.open(BLAH, '_blank')
        }

    return (
        <button onClick={handleBlah}> BLAHBLAH </button>
    )
}

My test using Jest:

it('should be able to render "BLAHBLAH " button ', () => {
    window.open = jest.fn();
    const BLAH = 'https://www.google.com/'
    const { getByText } = render(<Blah/>) // Get text by my page Blah
    const buttonGoToBlah = getByText('BLAHBLAH') // Get button by text
    fireEvent.click(buttonGoToBlah) // Simulate the click event

    expect(window.open).toHaveBeenCalledTimes(1) // Expect the window.open have to been called at least once.
    expect(window.open).toHaveBeenCalledWith(BLAH, '_blank'); // And the page should be the same called in my BLAH page
})

Upvotes: 0

Sagar
Sagar

Reputation: 4957

I'm directly assigning jest.fn() to window.open.

window.open = jest.fn()
// ...code
expect(window.open).toHaveBeenCalledTimes(1)
expect(window.open).toHaveBeenCalledWith('/new-tab','_blank')

Upvotes: 30

Thuy
Thuy

Reputation: 1663

const windowSpy = jest.spyOn(iFrame, "contentWindow", "get");
windowSpy.mockImplementation(() => ({
  location: {
    origin: "https://test.com",
    href: "href",
    hash: "hash"
  }
}));

Upvotes: 0

Alex Fallenstedt
Alex Fallenstedt

Reputation: 2091

I have a utility function which allows me to mock any method on the window like so:

  function givenMockWindowMethods(methods: Partial<{ [key in keyof Window]: jest.Mock<any, any> }>): () => void {
    const mocks = Object.values(methods);

    Object.entries(methods).forEach(([key, value]) => {
      Object.defineProperty(window, key, { value });
    });

    return (): void => mocks.forEach((mock) => mock?.mockClear());
  }

So if I need to mock the open method (or anything really) on the window, I can do:

      const cleanupMocks = givenMockWindowMethods({ open: jest.fn() });
      // expect(...).toBe(...)

      //at the end of the test, clean it up
      cleanupMocks()

Upvotes: 1

jmarceli
jmarceli

Reputation: 20182

There are a couple of ways to mock globals in Jest:

  1. Use the mockImplementation approach (the most Jest-like way), but it will work only for those variables which has some default implementation provided by jsdom. window.open is one of them:

    test('it works', () => {
  // Setup
  const mockedOpen = jest.fn();
  // Without making a copy, you will have a circular dependency problem
  const originalWindow = { ...window };
  const windowSpy = jest.spyOn(global, "window", "get");
  windowSpy.mockImplementation(() => ({
    ...originalWindow, // In case you need other window properties to be in place
    open: mockedOpen
  }));

  // Tests
  statementService.openStatementsReport(111)
  expect(mockedOpen).toBeCalled();

  // Cleanup
  windowSpy.mockRestore();
});

  2. Assign the value directly to the global property. It is the most straightforward, but it may trigger error messages for some window variables, e.g. window.href.

    test('it works', () => {
  // Setup
  const mockedOpen = jest.fn();
  const originalOpen = window.open;
  window.open = mockedOpen;

  // Tests
  statementService.openStatementsReport(111)
  expect(mockedOpen).toBeCalled();

  // Cleanup
  window.open = originalOpen;
});

  3. Don't use globals directly (requires a bit of refactoring)

    Instead of using the global value directly, it might be cleaner to import it from another file, so mocking will became trivial with Jest.

File ./test.js

jest.mock('./fileWithGlobalValueExported.js');
import { windowOpen } from './fileWithGlobalValueExported.js';
import { statementService } from './testedFile.js';

// Tests
test('it works', () => {
  statementService.openStatementsReport(111)
  expect(windowOpen).toBeCalled();
});

File ./fileWithGlobalValueExported.js

export const windowOpen = window.open;

File ./testedFile.js

import { windowOpen } from './fileWithGlobalValueExported.js';
export const statementService = {
  openStatementsReport(contactIds) {
    windowOpen(`a_url_${contactIds}`);
  }
}

Upvotes: 41

Alonad
Alonad

Reputation: 2256

In my component I need access to window.location.search. This is what I did in the Jest test:

Object.defineProperty(global, "window", {
  value: {
    location: {
      search: "test"
    }
  }
});

In case window properties must be different in different tests, we can put window mocking into a function, and make it writable in order to override for different tests:

function mockWindow(search, pathname) {
  Object.defineProperty(global, "window", {
    value: {
      location: {
        search,
        pathname
      }
    },
    writable: true
  });
}

And reset after each test:

afterEach(() => {
  delete global.window.location;
});

Upvotes: 22

serv-inc
serv-inc

Reputation: 38297

If it's similar to the window location problem at window.location.href can't be changed in tests. #890, you could try (adjusted):

delete global.window.open;
global.window = Object.create(window);
global.window.open = jest.fn();

Upvotes: 5

tvsbrent
tvsbrent

Reputation: 2619

The following method worked for me. This approach allowed me to test some code that should work both in the browser and in Node.js, as it allowed me to set window to undefined.

This was with Jest 24.8 (I believe):

let windowSpy;

beforeEach(() => {
  windowSpy = jest.spyOn(window, "window", "get");
});

afterEach(() => {
  windowSpy.mockRestore();
});

it('should return https://example.com', () => {
  windowSpy.mockImplementation(() => ({
    location: {
      origin: "https://example.com"
    }
  }));

  expect(window.location.origin).toEqual("https://example.com");
});

it('should be undefined.', () => {
  windowSpy.mockImplementation(() => undefined);

  expect(window).toBeUndefined();
});

Upvotes: 232

stefan
stefan

Reputation: 2785

In your Jest configuration, add setupFilesAfterEnv: ["./setupTests.js"], create that file, and add the code you want to run before the tests:

// setupTests.js
window.crypto = {
   .....
};

Reference: setupFilesAfterEnv [array]

Upvotes: 2

Jee Mok
Jee Mok

Reputation: 6566

I found an easy way to do it: delete and replace

describe('Test case', () => {
  const { open } = window;

  beforeAll(() => {
    // Delete the existing
    delete window.open;
    // Replace with the custom value
    window.open = jest.fn();
    // Works for `location` too, eg:
    // window.location = { origin: 'http://localhost:3100' };
  });

  afterAll(() => {
    // Restore original
    window.open = open;
  });

  it('correct url is called', () => {
    statementService.openStatementsReport(111);
    expect(window.open).toBeCalled(); // Happy happy, joy joy
  });
});

Upvotes: 9

abhishek khandait
abhishek khandait

Reputation: 2157

You can try this:

import * as _Window from "jsdom/lib/jsdom/browser/Window";

window.open = jest.fn().mockImplementationOnce(() => {
    return new _Window({ parsingMode: "html" });
});

it("correct url is called", () => {
    statementService.openStatementsReport(111);
    expect(window.open).toHaveBeenCalled();
});

Upvotes: 5

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