@Test
public void testRemoveSource() {

    mSource.setValue("flatfoot");
    Observer observer = mock(Observer.class);
    mMediator.addSource(mSource, observer);
    verify(observer).onChanged("flatfoot");
    mMediator.removeSource(mSource);
    reset(observer);
    mSource.setValue("failure");
    verify(observer, never()).onChanged(any());
}