Building a new root component

The Git tag for this section is root-component.

After all that setup, we're now ready to build App, the component that ties everything else together. As a reminder, this component will implement our workflow, switching between three screens:

• Initially, it will show the AppointmentsDayViewLoader, along with a button
• If the user clicks the button, they will be shown the CustomerForm
• Once they've completed that form and submitted the customer to the server, the user will be shown the AppointmentFormLoader and can then book an appointment
• Once the appointment has been booked, the user is taken back to viewing the AppointmentsDayViewLoader

Let's get started:

1. Create a new file, test/App.test.js, with the following setup and the first test:

import React from 'react';
import {
  createShallowRenderer,
  type
} from './shallowHelpers...