Adding items to the shopping cart

Once we have the basic structure of the ShoppingCart component, we need to add a few more assertions to verify it works. We will start by adding one item to the cart, which can be done with the following code:

it('adds menu item to shopping cart', () => {
  render(<PizzaShopApp />);
  const menuList = screen.getByRole('list');
  const menuItems = within(menuList).getAllByRole('listitem');
  const addButton = within(menuItems[0]).getByRole('button');
  userEvent.click(addButton);
  const shoppingCartContainer = screen.getByTestId('shopping-cart');
  const placeOrderButton = within(shoppingCartContainer).
   getByRole('button');
  expect(within(shoppingCartContainer).getByText('Margherita Pizza')).
   toBeInTheDocument();
  expect(placeOrderButton).toBeEnabled...