the empty string after load if playing a MediaSource from the src attribute");
      next();
    });
  },
  function() {
    fetch('/media/sound_0.mp3')
      .then(function(response) {
        return response.arrayBuffer();
      }).then((b) => {
        v.src = URL.createObjectURL(new Blob([new Uint8Array(b)], ["audio/mpeg"]));
        queueTaskAndStep(function() {
          assert_not_equals(v.currentSrc, "", "currentSrc must be not equal to the empty string after load if playing a Blob from the src attr