test: add test case

tests/renderer/state-spec.ts

@@ -1,6 +1,8 @@
 import { reaction } from 'mobx';
 
 import {
+  AppStateBroadcastChannel,
+  AppStateBroadcastMessageType,
   BlockableAccelerator,
   ElectronReleaseChannel,
   GenericDialogType,
@@ -743,4 +745,28 @@ describe('AppState', () => {
       expect(actual).toBe(expected);
     });
   });
+
+  describe('broadcastChannel', () => {
+    it('updates the version state in response to changes in other windows', async () => {
+      const broadcastChannel: AppStateBroadcastChannel = new BroadcastChannel(
+        'AppState',
+      );
+
+      const fakeVersion = {
+        version: '13.9.9',
+        state: InstallState.downloading,
+      } as RunnableVersion;
+
+      expect(appState.versions[fakeVersion.version]).toBeFalsy();
+
+      broadcastChannel.postMessage({
+        type: AppStateBroadcastMessageType.syncVersions,
+        payload: [fakeVersion],
+      });
+
+      expect(appState.versions[fakeVersion.version].state).toEqual(
+        InstallState.downloading,
+      );
+    });
+  });
 });

tests/setup.js

@@ -32,9 +32,26 @@ jest.mock('@sentry/electron/renderer', () => ({
   init: jest.fn(),
 }));
 
-global.BroadcastChannel = class {
-  addEventListener = jest.fn();
-  postMessage = jest.fn();
+class FakeBroadcastChannel {
+  listeners = [];
+
+  addEventListener = (_, callback) => {
+    this.listeners.push(callback);
+  };
+
+  postMessage = (message) => {
+    for (const listener of this.listeners) {
+      listener(new MessageEvent('message', { data: message }));
+    }
+  };
+}
+
+global.BroadcastChannel = class Singleton {
+  static instance = new FakeBroadcastChannel();
+
+  constructor(_) {
+    return Singleton.instance;
+  }
 };
 
 expect.addSnapshotSerializer(createSerializer({ mode: 'deep' }));