localStorage test configuration

index.test.tsx

describe('testing localStorage', () => {
  // This following snippet is from https://amitd.co/code/testing/spying-on-localstorage-in-jest 
  // Thank you so much Amit Dhamu for this implementation

  jest.spyOn(Object.getPrototypeOf(window.localStorage), 'setItem');
  Object.setPrototypeOf(window.localStorage.setItem, jest.fn());

  it('saves to localStorage when clicked on button', () => {
    render(<Component />);
    
    const button = screen.getByRole('button');

    fireEvent.click(button);

    expect(window.localStorage.setItem).toHaveBeenCalledWith('key', '{\"hello\": \"world\"}')
  })

index.tsx

interface Data {
  hello: string;
}

function Component() {
  const handleSaveToLocalStorage = (data: Data) => {
    localStorage.setItem('key', JSON.stringify(data))
  }

  return (
    <div>
      <button onClick={() => handleSaveToLocalStorage({hello: 'world'})}>
         Save Data to localStorage
      </button>
    </div>
  )
}

export default Component