Vue JS - Unit test - localstorage is not defined - unit-testing

Question

I'm writing unit test for for vue cli 3 using Mocha and chai. I have tried mocking localstorage. but still getting this error - 'localStorage is not defined'. Can anyone please help me here?
My code is like this -
import { expect, assert } from 'chai';
import { shallowMount } from '#vue/test-utils';
import LoginComponent from '#/views/LoginComponent.vue';
import Constants from '#/constants';
declare var global: any;
let wrapper;
let componentInstance: any;
let authData;
var mockLocalStorage = {
getItem(key: any) {
if (key === 'access_token') { return '/* a token object */'; }
return 'null';
}
};
describe('LoginComponent.vue', () => {
beforeEach(() => {
global.window = { localStorage: mockLocalStorage };
authData = JSON.stringify(Constants.AUTH_DATA);
wrapper = shallowMount(AliUMSLoginComponent, {
propsData: { authData }
});
componentInstance = wrapper.vm;
});
it('has a created hook', () => {
assert.isNotNull(componentInstance.authData);
});
});

Answer 1

For anyone else who might stumble upon this question - the following worked for me:
1) Create a setup.js file in your unit test folder and add the following code:
require('jsdom-global')();
global.localStorage = window.localStorage;
After fixing the "localStorage is undefined" error, you might experience additional errors (like I did). In the end the following code snippet fixed everything:
require('jsdom-global')(undefined, { url: 'https://localhost' });
global.localStorage = window.localStorage;
global.sessionStorage = window.sessionStorage;
window.Date = Date;
... You can find more info on this here: vuejs/vue-cli/issues/2128 and here: vuejs/vue-test-utils/issues/936
2) Update the test script in your package.json file to load the setup file you just created:
"test:unit": "vue-cli-service test:unit --require tests/unit/setup.js"

Answer 2

I got your solution to work however when trying to grep for one file to run, it runs all files.
Is there a better way to include this maybe with an include at the top of the file? An include usually has a method that returns something. hmmmm how to do this?
Is this the correct syntax for the package.json file:
"test:unit-filter": "vue-cli-service test:unit --require tests/unit/helpers/setup.js --watch --grep"