Add a PeerConnection integration test for adding an audio track mid-call

webrtc/pc/peerconnection_integrationtest.cc

Index: webrtc/pc/peerconnection_integrationtest.cc
diff --git a/webrtc/pc/peerconnection_integrationtest.cc b/webrtc/pc/peerconnection_integrationtest.cc
index d20e2f965b5a43cbaf543689a97c2bd4b67dcf29..6b3ddd55bff4fb4ca58ef5b3757df3fb726c06b2 100644
--- a/webrtc/pc/peerconnection_integrationtest.cc
+++ b/webrtc/pc/peerconnection_integrationtest.cc
@@ -1393,8 +1393,7 @@ TEST_F(PeerConnectionIntegrationTest, AudioToVideoUpgrade) {
   // Initially, offer an audio/video stream from the caller, but refuse to
   // send/receive video on the callee side.
   caller()->AddAudioVideoMediaStream();
-  callee()->AddMediaStreamFromTracks(callee()->CreateLocalAudioTrack(),
-                                     nullptr);
+  callee()->AddAudioOnlyMediaStream();
   PeerConnectionInterface::RTCOfferAnswerOptions options;
   options.offer_to_receive_video = 0;
   callee()->SetOfferAnswerOptions(options);
@@ -1425,6 +1424,30 @@ TEST_F(PeerConnectionIntegrationTest, AudioToVideoUpgrade) {
       kMaxWaitForFramesMs);
 }
 
+// Simpler than the above test; just add an audio track to an established
+// video-only connection.
+TEST_F(PeerConnectionIntegrationTest, AddAudioToVideoOnlyCall) {
+  ASSERT_TRUE(CreatePeerConnectionWrappers());
+  ConnectFakeSignaling();
+  // Do initial offer/answer with just a video track.
+  caller()->AddVideoOnlyMediaStream();
+  callee()->AddVideoOnlyMediaStream();
+  caller()->CreateAndSetAndSignalOffer();
+  ASSERT_TRUE_WAIT(SignalingStateStable(), kDefaultTimeout);
+  // Now add an audio track and do another offer/answer.
+  caller()->AddMediaStreamFromTracksWithLabel(caller()->CreateLocalAudioTrack(),
+                                              nullptr, "audio_stream");
+  callee()->AddMediaStreamFromTracksWithLabel(callee()->CreateLocalAudioTrack(),
+                                              nullptr, "audio_stream");
+  caller()->CreateAndSetAndSignalOffer();
+  ASSERT_TRUE_WAIT(SignalingStateStable(), kDefaultTimeout);
+  // Ensure both audio and video frames are received end-to-end.
+  ExpectNewFramesReceivedWithWait(
+      kDefaultExpectedAudioFrameCount, kDefaultExpectedVideoFrameCount,
+      kDefaultExpectedAudioFrameCount, kDefaultExpectedVideoFrameCount,
+      kMaxWaitForFramesMs);
+}
+
 // This test sets up a call that's transferred to a new caller with a different
 // DTLS fingerprint.
 TEST_F(PeerConnectionIntegrationTest, CallTransferredForCallee) {