Test-driving a WebSocket connection

We start by filling out that first function, startSharing. This function is invoked when the START_SHARING action is received. That action is triggered when the user clicks the Start sharing button:

1. Open test/middleware/sharingSagas.test.js and add the following imports at the top:

   import { storeSpy, expectRedux } from "expect-redux";
   import { act } from "react-dom/test-utils";
   import { configureStore } from "../../src/store";

2. At the bottom of the file, add a new describe block and its setup. We’ll break this into a couple of steps: first, set up the Redux store and the WebSocket spy. Because window.WebSocket is a constructor function, we use mockImplementation to stub it out:

   describe("sharingSaga", () => {
     let store;
     let socketSpyFactory;
     beforeEach(() => {
       store = configureStore([storeSpy]);
       socketSpyFactory...