### Question:
VoiceCallEngine { public void muteMic() { mRtcEngine.muteLocalAudioStream(true); } private  VoiceCallEngine(); static VoiceCallEngine getInstance(); RtcEngine getmRtcEngine(); void joinChannel(String channelID, EventHandler handler); void leaveChannel(); void muteMic(); void unmuteMic(); void useSpeaker(); void useEarpiece();  }### Answer:
@Test public void testMuteMic() { VoiceCallEngine.getInstance().muteMic(); verify(VoiceCallEngine.getInstance().getmRtcEngine(), times(1)).muteLocalAudioStream(true); }