Espresso测试在设备（而不是模拟器）上失败

Question

我运行Espresso测试只是为了测试RecyclerView中视图的点击以及RecyclerView视图中的文本。

该测试通过了我的Genymotion模拟器，但在我的设备（Google Nexus 6）上失败了，并且我无法找出原因：

@RunWith(AndroidJUnit4.class)
public class EspressoTest {


    @Rule
    public ActivityTestRule<MainActivity> firstRule = new ActivityTestRule<>(MainActivity.class);


    @Test
    public void testRecyclerViewClick() {
        Espresso.onView(ViewMatchers.withId(R.id.recycler_view_ingredients)).perform(RecyclerViewActions.actionOnItemAtPosition(0, click()));
    }

    //TODO: This test is not passing on my device, but it is passing on an emulator. I am not sure why, but have read about idling resources. Can you confirm how to handle?
    @Test
    public void testRecyclerViewText(){
        Espresso.onView(ViewMatchers.withId(R.id.recycler_view_ingredients)).perform(RecyclerViewActions.scrollToPosition(0));
        Espresso.onView(withText("Nutella Pie")).check(matches(isDisplayed()));
    }

}