@Test
public void push_removesPreviousFromTree() {

    assertNotChildOf(uut.getView(), child1.getView());
    uut.push(child1, new CommandListenerAdapter());
    assertIsChild(uut.getView(), child1.getView());
    uut.push(child2, new CommandListenerAdapter() {
        @Override
        public void onSuccess(String childId) {
            assertThat((View) uut.getView().findViewById(child1.getView().getId())).isNull();
            assertThat((View) uut.getView().findViewById(child2.getView().getId())).isNotNull();
        }
    });
}