Simulating window.location in TypeScript jest test

Question

Simulating window.location in TypeScript jest test

In my code snippet, I have a function that constructs a complete URL for redirection:

import { redirect } from './some-utils'

export const goToURL = () => {
    const url = window.location.origin + window.location.pathname
    redirect(url)
}

Now, I am attempting to create a TypeScript test to verify the correctness of the URL string:

describe('my-test-file', () => {
    let originalWindowLocation
    const redirect = jest.fn()

    beforeEach(() => {
        jest.resetAllMocks()
        originalWindowLocation = window.location
    })

    afterEach(() => {
        window.location = originalWindowLocation
    })

    it('should validate the redirected URL', () => {
        delete window.location // cannot proceed due to TS error
        window.location = { origin: 'https://www.example.com', pathname: '/mypath' } // facing TS complaint

        goToURL()
        expect(redirect).toHaveBeenCalledTimes(1)
        expect(redirect).toHaveBeeenCalledWith('https://www.example.com/mypath')
    })
})

However, encountering two TypeScript errors. Firstly, on the delete line:

The operand of a 'delete' operator must be optional.

And secondly, during the assignment of window.location:

Type '{ origin: string; pathname: string; }' is not assignable to type 'Location | (string & Location)'. Type '{ origin: string; pathname: string; }' is not assignable to type 'string & Location'. Type '{ origin: string; pathname: string; }' is not assignable to type 'string'.

My attempts at rectifying these issues by altering the code did remove the TS errors, but the test no longer passes as expected. It seems to utilize the domain of my application rather than the specified one in the test.

Would appreciate any assistance in resolving the TypeScript errors while ensuring successful test execution.

Edit:

Even trying

window.location = 'https://www.example.com/mypath'

does not resolve the issue and results in a TS error:

Type 'string' is not assignable to type 'Location | (string & Location)'

Using

window.location.href = 'https://www.example.com/mypath'

resolves the TS errors, but the test outcome remains unchanged.

Similarly, with

window.location.assign(https://www.example.com/mypath')

, the TS errors disappear but the test result stays the same.

typescript jestjs

Answer 1

Answer №1

If you're utilizing just a portion of the Location API that is also found on an instance of URL (for example,

window.location.href = "https://domain.tld/pathname"

), you can manually mock (replace) that property on window during your testing:

describe('description', () => {
  let originalWindowLocation = window.location;

  beforeEach(() => {
    Object.defineProperty(window, 'location', {
      configurable: true,
      enumerable: true,
      value: new URL(window.location.href),
    });
  });

  afterEach(() => {
    Object.defineProperty(window, 'location', {
      configurable: true,
      enumerable: true,
      value: originalWindowLocation,
    });
  });

  it('test that redirection URL is correct', () => {
    const expectedUrl = 'https://www.example.com/mypath';
    window.location.href = expectedUrl;
    expect(window.location.href).toBe(expectedUrl);
  });
});

I intentionally focused only on the specific issue you raised about mocking a function invocation within a closure from an external module. If you need to mock such a scenario with functions like redirect and goToURL, refer to Jest's documentation on mocking modules and mocking partials.

Answer 2

If you're utilizing just a portion of the Location API that is also found on an instance of URL (for example,

window.location.href = "https://domain.tld/pathname"

), you can manually mock (replace) that property on window during your testing:

describe('description', () => {
  let originalWindowLocation = window.location;

  beforeEach(() => {
    Object.defineProperty(window, 'location', {
      configurable: true,
      enumerable: true,
      value: new URL(window.location.href),
    });
  });

  afterEach(() => {
    Object.defineProperty(window, 'location', {
      configurable: true,
      enumerable: true,
      value: originalWindowLocation,
    });
  });

  it('test that redirection URL is correct', () => {
    const expectedUrl = 'https://www.example.com/mypath';
    window.location.href = expectedUrl;
    expect(window.location.href).toBe(expectedUrl);
  });
});

I intentionally focused only on the specific issue you raised about mocking a function invocation within a closure from an external module. If you need to mock such a scenario with functions like redirect and goToURL, refer to Jest's documentation on mocking modules and mocking partials.

Answer 3

Answer №2

Alternative Approach to Testing window.location.assign

This method has worked well for me.

While it may be tempting to directly manipulate window.location or window.location.href, this can create difficulties when testing your code.

Testing tip #1: Make sure your code is testable in order to effectively debug and maintain it.

To address this issue, consider utilizing window.location.assign(url) in your application logic instead.

During testing, you can validate the behavior by spying on the assign method like this:

let assignSpy = jest.spyOn(window.location, 'assign')

// ...set up, execute

expect(assignSpy).toHaveBeenCalledWith( expectedUrl )

Your tests should focus on verifying the assigned URL, rather than directly checking window.location or window.location.href. By leveraging the assign method and spying capabilities, you can ensure both functionality and testability in your code.

Answer 4

Alternative Approach to Testing window.location.assign

This method has worked well for me.

While it may be tempting to directly manipulate window.location or window.location.href, this can create difficulties when testing your code.

Testing tip #1: Make sure your code is testable in order to effectively debug and maintain it.

To address this issue, consider utilizing window.location.assign(url) in your application logic instead.

During testing, you can validate the behavior by spying on the assign method like this:

let assignSpy = jest.spyOn(window.location, 'assign')

// ...set up, execute

expect(assignSpy).toHaveBeenCalledWith( expectedUrl )

Your tests should focus on verifying the assigned URL, rather than directly checking window.location or window.location.href. By leveraging the assign method and spying capabilities, you can ensure both functionality and testability in your code.

Simulating window.location in TypeScript jest test

Answer №1

Answer №2

Alternative Approach to Testing window.location.assign

Similar questions

Tips for stopping webpack from creating compiled files in the source directory

Issue with Codemirror lint functionality not functioning properly in a React/Redux/Typescript application

There appears to be an issue with the compilation of the TypeScript "import { myVar }" syntax in a Node/CommonJS/ES5 application

Mismatch between generic types

Retrieve the name of a property or field from an object with a specified type

What is the best way to showcase a global variable in Typescript using HTML?

Increase the vertical distance between rows in a table

Is type inference a trustworthy method?

An unconventional approach to conducting runtime checks on Typescript objects

Issue: Express, Mocha, and Chai Error - Server is not running

It appears that React Native's absolute paths are not functioning as expected

React Redux Saga doesn't trigger any actions

What is the process of invoking a function in Typescript?

What is the most effective way to retrieve cursors from individual entities in a Google Cloud Datastore query?

Reducer incorporating nested array mappings

The function parameter in Angular's ngModelChange behaves differently than $event

Changing an object in the Mongoose pre-save hook

What is the best way to loop through an object in TypeScript and replace a string value with its corresponding number?

What is the process for importing a .webp file into a TypeScript file to be utilized in an Angular project down the line?

Issue with Supabase join function: only returning a single object instead of a list of objects