The dependency on hardware devices could be eliminated by using a fake CrasAudioClient (like in CrasAudioHandlerTest https://cs.chromium.org/chromium/src/chromeos/audio/cras_audio_handler_unittest.cc). Tests would catch regressions like  issue 764228 . Wu-cheng pointed out that none of the CQ bots could run such a test, since none use CrAS (there is a Chrome OS-on-Linux bot, but it's using either AudioManagerAlsa or AudioManagerPulse). A real Chrome OS bot would thus also be needed.