updating src/setupTests.js example

Created by: jacobpatterson1549

Updating the assignment localStorageMock to the 'global' object in example.

The mock object is not set correctly when the assignment operator ('=') is used. When running the test below with the previous 'src/setupTest.js' example, I get the error "window.localStorage.getItem.mockReturnValue is not a function." When 'Object.defineProperty' replaces the assignment in 'src/setupTest.js,' the test passes.

import '@testing-library/jest-dom';
import { render, screen } from '@testing-library/react';

it('should get the item', () => {
    const MockComponent = () => (
        <p>{global.localStorage.getItem('test')}</p>
    );
    const expected = 'juicy';
    global.localStorage.getItem.mockReturnValue(expected);
    render(<MockComponent />);
    const element = screen.getByText(expected);
    expect(element).toBeInTheDocument();
    expect(global.localStorage.getItem).toBeCalled();
});