add a unit test for connect() method of SlackWebSocket

Author: Filip Maj

packages/socket-mode/package.json

@@ -57,11 +57,13 @@
     "@tsconfig/recommended": "^1.0.7",
     "@types/chai": "^4",
     "@types/mocha": "^10",
+    "@types/proxyquire": "^1.3.31",
     "@types/sinon": "^17",
     "c8": "^10.1.2",
     "chai": "^4",
     "mocha": "^10",
     "nodemon": "^3.1.0",
+    "proxyquire": "^2.1.3",
     "shx": "^0.3.2",
     "sinon": "^19",
     "source-map-support": "^0.5.21",

packages/socket-mode/src/SlackWebSocket.spec.ts

@@ -1,14 +1,29 @@
 import { ConsoleLogger } from '@slack/logger';
 import { assert } from 'chai';
 import EventEmitter from 'eventemitter3';
+import proxyquire from 'proxyquire';
 import sinon from 'sinon';
-
-import { SlackWebSocket } from './SlackWebSocket';
+proxyquire.noPreserveCache();
 import logModule from './logger';
 
+// A slightly spruced up event emitter aiming at mocking out the `ws` library's `WebSocket` class
+class WSMock extends EventEmitter {
+  // biome-ignore lint/suspicious/noExplicitAny: event listeners can accept any args
+  addEventListener(evt: string, fn: (...args: any[]) => void) {
+    this.addListener.call(this, evt, fn);
+  }
+}
+
 describe('SlackWebSocket', () => {
   const sandbox = sinon.createSandbox();
-
+  let SlackWebSocket: typeof import('./SlackWebSocket').SlackWebSocket;
+  beforeEach(() => {
+    SlackWebSocket = proxyquire.load('./SlackWebSocket', {
+      ws: {
+        WebSocket: WSMock,
+      },
+    }).SlackWebSocket;
+  });
   afterEach(() => {
     sandbox.restore();
   });
@@ -38,4 +53,31 @@ describe('SlackWebSocket', () => {
       assert.isFalse(logFactory.called);
     });
   });
+  describe('WebSocket event handling', () => {
+    it('should call disconnect() if websocket emits an error', async () => {
+      // an exposed event emitter pretending its a websocket
+      const ws = new WSMock();
+      // mock out the `ws` library and have it return our event emitter mock
+      SlackWebSocket = proxyquire.load('./SlackWebSocket', {
+        ws: {
+          WebSocket: class Fake {
+            constructor() {
+              // biome-ignore lint/correctness/noConstructorReturn: for test mocking purposes
+              return ws;
+            }
+          },
+        },
+      }).SlackWebSocket;
+      const sws = new SlackWebSocket({
+        url: 'whatevs',
+        client: new EventEmitter(),
+        clientPingTimeoutMS: 1,
+        serverPingTimeoutMS: 1,
+      });
+      const discStub = sinon.stub(sws, 'disconnect');
+      sws.connect();
+      ws.emit('error', { error: new Error('boom') });
+      sinon.assert.calledOnce(discStub);
+    });
+  });
 });

packages/socket-mode/test/integration.spec.js

@@ -132,7 +132,7 @@ describe('Integration tests with a WebSocket server', () => {
   });
   describe('unexpected socket messages sent to client', () => {
     const debugLoggerSpy = sinon.stub(); // add the following to expose further logging: .callsFake(console.log);
-    const noop = () => { };
+    const noop = () => {};
     beforeEach(() => {
       client = new SocketModeClient({
         appToken: 'whatever',