@Test
 public void testUpdateDataSet() throws IllegalAccessException, NoSuchFieldException {
   chatActivity.onResume();
   chatActivity.showMessage("test");
   assertTrue(recyclerView.hasPendingAdapterUpdates());
   chatActivity.updateDataSet();
   // assertFalse(recyclerView.hasPendingAdapterUpdates());
   chatActivity.onStop();
 }
 @Override
 public void onResume() {
   super.onResume();
   signaller.setObserver(this);
 }