Jest sessionstorage is not defined

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When encountering the error “jest sessionstorage is not defined”, it means that the sessionStorage object is not recognized or available within the context of your Jest tests.

Jest is a popular JavaScript testing framework that runs in Node.js, where sessionStorage is not natively supported as it is a browser-specific feature. Since Jest runs tests in a Node.js environment, it does not have access to DOM-specific objects and APIs like sessionStorage.

However, you can simulate the behavior of sessionStorage in your Jest tests using various techniques. One common approach is to use a mock or a polyfill to provide a fake implementation of the sessionStorage object.

Here’s an example of how you can achieve this:


// mock-sessionstorage.js

const sessionStorageMock = {
  getItem: jest.fn(),
  setItem: jest.fn(),
  removeItem: jest.fn(),
  clear: jest.fn()
};

Object.defineProperty(window, 'sessionStorage', {
  value: sessionStorageMock
});

// your-test-file.js

import { getItemFromSessionStorage } from './your-module';

describe('getItemFromSessionStorage', () => {
  it('should retrieve an item from sessionStorage', () => {
    sessionStorage.setItem('key', 'value');

    const result = getItemFromSessionStorage('key');

    expect(window.sessionStorage.getItem).toHaveBeenCalledWith('key');
    expect(result).toEqual('value');
  });
});

In the above example, we create a mock object for the sessionStorage API with the help of Jest’s provided mock functions. Then, we assign this mock object to the global window object using Object.defineProperty. This way, whenever your code references sessionStorage, it will actually use the mock object instead.

Now, you can write tests for functions that interact with sessionStorage, such as getItemFromSessionStorage in the example. Inside the test, you can use the mocked sessionStorage API to set an item and then verify the behavior of your code.

Remember to import and use the appropriate mocked object in your test file and any other modules that rely on sessionStorage.

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