fix: failing test in App.test.js (#296)

Author: huyenltnguyen

src/components/App.test.js

@@ -1,27 +1,6 @@
 import React from 'react';
 import ReactDOM from 'react-dom';
 import App from './App';
-import * as utils from '../utils/buildEventSource';
-
-const buildEventSourceSpy = jest.spyOn(utils, 'buildEventSource');
-
-buildEventSourceSpy.mockReturnValue({
-  CLOSED: 0,
-  CONNECTING: 0,
-  OPEN: 0,
-  dispatchEvent(event) {
-    return false;
-  },
-  onerror: jest.fn(),
-  onmessage: jest.fn(),
-  onopen: jest.fn(),
-  readyState: 0,
-  url: '',
-  withCredentials: false,
-  addEventListener: jest.fn(),
-  close: jest.fn(),
-  removeEventListener: jest.fn()
-});
 
 it('renders without crashing', () => {
   const div = document.createElement('div');

src/setupTests.js

@@ -1 +1,22 @@
 import '@testing-library/jest-dom';
+
+Object.defineProperty(window, 'EventSource', {
+  writable: true,
+  value: jest.fn().mockImplementation(() => ({
+    CLOSED: 0,
+    CONNECTING: 0,
+    OPEN: 0,
+    dispatchEvent(event) {
+      return false;
+    },
+    onerror: jest.fn(),
+    onmessage: jest.fn(),
+    onopen: jest.fn(),
+    readyState: 0,
+    url: '',
+    withCredentials: false,
+    addEventListener: jest.fn(),
+    close: jest.fn(),
+    removeEventListener: jest.fn()
+  }))
+});