关于录屏相关的消息格式需要封一层，放在on-message下，利用on-message传递

client/test/unit/signaling.test.js

@@ -43,6 +43,89 @@ function createWebSocketSignaling(port) {
   return new WebSocketSignaling(1, `ws://localhost:${port}`);
 }
 
+describe('recording signaling message envelope', () => {
+  const OriginalWebSocket = window.WebSocket;
+  let sentMessages;
+
+  beforeEach(() => {
+    sentMessages = [];
+    window.WebSocket = class {
+      constructor() {
+        this.readyState = 1;
+      }
+
+      send(message) {
+        sentMessages.push(message);
+      }
+
+      close() {
+        if (this.onclose) {
+          this.onclose();
+        }
+      }
+    };
+  });
+
+  afterEach(() => {
+    window.WebSocket = OriginalWebSocket;
+  });
+
+  test('sends recording offer through on-message', () => {
+    const signaling = new WebSocketSignaling(1, 'ws://localhost:1234');
+
+    signaling.sendRecordingOffer({
+      recordingId: 'recording-1',
+      connectionId: 'room-1',
+      participantId: 'participant-1',
+      sdp: 'offer-sdp'
+    });
+
+    expect(sentMessages).toHaveLength(1);
+    const outer = JSON.parse(sentMessages[0]);
+    expect(outer.type).toBe('on-message');
+    expect(outer.data.connectionId).toBe('room-1');
+    expect(outer.data.message).toEqual({
+      type: 'recording-offer',
+      data: {
+        recordingId: 'recording-1',
+        connectionId: 'room-1',
+        participantId: 'participant-1',
+        sdp: 'offer-sdp'
+      }
+    });
+  });
+
+  test('dispatches wrapped recording messages as recording events', () => {
+    const signaling = new WebSocketSignaling(1, 'ws://localhost:1234');
+    let recordingAnswer;
+    signaling.addEventListener('recording-answer', (event) => {
+      recordingAnswer = event.detail;
+    });
+
+    signaling.websocket.onmessage({
+      data: JSON.stringify({
+        type: 'on-message',
+        from: 'room-1',
+        data: JSON.stringify({
+          type: 'recording-answer',
+          data: {
+            recordingId: 'recording-1',
+            connectionId: 'room-1',
+            sdp: 'answer-sdp'
+          }
+        })
+      })
+    });
+
+    expect(recordingAnswer).toEqual({
+      type: 'recording-answer',
+      recordingId: 'recording-1',
+      connectionId: 'room-1',
+      sdp: 'answer-sdp'
+    });
+  });
+});
+
 describe.each(signalingModes)('signaling test in public mode', ({ mode }) => {
   let signaling1;
   let signaling2;