jest-localstorage-mock

What is jest-localstorage-mock?

The jest-localstorage-mock package is a Jest mock for the localStorage API, allowing developers to test code that interacts with localStorage without relying on the actual browser implementation. This can help ensure tests are isolated and run consistently across different environments.

What are jest-localstorage-mock's main functionalities?

Mocking localStorage

This feature allows you to mock the localStorage API, enabling you to test interactions with localStorage without relying on the actual browser implementation. The code sample demonstrates how to set an item in localStorage and verify that it was set correctly.

const localStorageMock = require('jest-localstorage-mock');

// Example test
it('should store an item in localStorage', () => {
  localStorage.setItem('key', 'value');
  expect(localStorage.setItem).toHaveBeenCalledWith('key', 'value');
  expect(localStorage.getItem('key')).toBe('value');
});

Clearing localStorage

This feature allows you to clear the localStorage, which is useful for ensuring a clean state between tests. The code sample demonstrates setting an item in localStorage and then clearing it, verifying that the item is no longer present.

const localStorageMock = require('jest-localstorage-mock');

// Example test
it('should clear localStorage', () => {
  localStorage.setItem('key', 'value');
  localStorage.clear();
  expect(localStorage.getItem('key')).toBeNull();
});

Removing an item from localStorage

This feature allows you to remove a specific item from localStorage. The code sample demonstrates setting an item in localStorage, removing it, and verifying that it has been removed.

const localStorageMock = require('jest-localstorage-mock');

// Example test
it('should remove an item from localStorage', () => {
  localStorage.setItem('key', 'value');
  localStorage.removeItem('key');
  expect(localStorage.getItem('key')).toBeNull();
});

Other packages similar to jest-localstorage-mock

localstorage-memory

localstorage-memory is an in-memory implementation of the localStorage API. It can be used in Node.js environments to simulate localStorage without relying on a browser. Compared to jest-localstorage-mock, localstorage-memory is more focused on providing a full in-memory localStorage implementation rather than just mocking it for tests.

node-localstorage

node-localstorage is a package that provides a localStorage implementation for Node.js. It writes data to disk, making it persistent across sessions. This is different from jest-localstorage-mock, which is designed specifically for mocking localStorage in tests and does not provide persistence.

mock-local-storage

mock-local-storage is another package that mocks the localStorage and sessionStorage APIs for testing purposes. It is similar to jest-localstorage-mock but also includes support for sessionStorage, providing a more comprehensive solution for testing storage APIs.

README

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Install

For yarn:

yarn add --dev jest-localstorage-mock

For npm:

npm i --save-dev jest-localstorage-mock

Setup

Require module directly

In your package.json under the jest section add the setupFiles attribute with this module name.

"jest": {
  "setupFiles": [
    "jest-localstorage-mock"
  ]
}

Use setup file

Alternatively you can create a new setup file and require this module.

__setups__/localstorage.js

global.chrome = require('jest-localstorage-mock');

And add that file to your setupFiles:

"jest": {
  "setupFiles": [
    "./__setups__/localstorage.js"
  ]
}

Usage

With this module setup in Jest you can run your web tests that rely on localstorage without fail.

Development

yarn install
yarn test

Pull Request

Before every PR run the following:

yarn run prettier

Publish

When publishing a new build, run the following:

yarn run prettier
yarn run build
yarn publish