Streaming events with redux-saga

We'll repeat a lot of the same techniques in this section. There are two new concepts: first, pulling out the search param for the watcher ID, and second, using eventChannel to subscribe to the WebSocket onmessage callback:

1. Write a new describe block at the bottom of test/middleware/sharingSagas.test.js, but still nested inside the main describe block:

describe('watching', () => {
  beforeEach(() => {
    Object.defineProperty(window, 'location', {
      writable: true,
      value: {
        host: 'test:1234',
        pathname: '/index.html',
        search: '?watching=234'
      }
    });
  });

  it('opens a socket when the page loads', () => {
    store.dispatch({ type: 'TRY_START_WATCHING' });
    expect(socketSpyFactory).toHaveBeenCalledWith(
      'ws://test:1234...