java - 为什么在 Mockito 测试期间源代码另有说明时 protected 最终字段为空？

Question

我使用 Mockito 1.10.19 创建了用于测试自定义 RecyclerView 适配器的测试。 (代码已经简化以消除信息噪音，留下最简单的版本仍然有问题)

public class CustomAdapter extends RecyclerView.Adapter<CustomViewHolder> {

    private final Dependency dependency;

    public CustomAdapter(@NonNull Dependency dependency) {
        this.dependency = dependency;
    }

    public void refreshData() {
        dependency.refreshData();
        notifyDataSetChanged();
    }

    @Override
    public CustomViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.ingredients_item, parent, false);
        return new CustomViewHolder(view);
    }

    @Override
    public void onBindViewHolder(CustomViewHolder holder, int position) {
        dependency.bind(holder, position);
    }

    @Override
    public int getItemCount() {
        return dependency.getItemsCount();
    }
}

我已经向它注入(inject)了模拟依赖项，但适配器在其他方面没有受到影响。

@RunWith(MockitoJUnitRunner.class)
public class CustomAdapterTest {

    private CustomAdapter adapter;
    @Mock
    private Dependecy dependencyMock;

    @Before
    public void setUp() throws Exception {
        adapter = new CustomAdapter(dependencyMock);
    }

    @Test
    public void testRefreshData() throws Exception {
        adapter.refreshData();
        verify(dependencyMock).refreshData();
        verifyNoMoreInteractions(dependencyMock);
    }
}

当运行非常简单的测试“testRefreshData()”适配器调用时 notifyDataSetChanged() .这导致 NullPointerException被抛出。

在 android.support.v7.widget.RecyclerView$AdapterDataObservable.notifyChanged(RecyclerView.java:10763)在 android.support.v7.widget.RecyclerView$Adapter.notifyDataSetChanged(RecyclerView.java:6342)

这发生在代码中:

static class AdapterDataObservable extends Observable<AdapterDataObserver> {
    public boolean hasObservers() {
        return !mObservers.isEmpty();
    }
public void notifyChanged() {
    // since onChanged() is implemented by the app, it could do anything, including
    // removing itself from {@link mObservers} - and that could cause problems if
    // an iterator is used on the ArrayList {@link mObservers}.
    // to avoid such problems, just march thru the list in the reverse order.
    for (int i = mObservers.size() - 1; i >= 0; i--) {
        mObservers.get(i).onChanged();
    }
}

取消引用时 mObservers .这不应该发生，因为 Observable<T>定义 mObservers作为最终和初始化:

public abstract class Observable<T> {
    /**
     * The list of observers.  An observer can be in the list at most
     * once and will never be null.
     */
    protected final ArrayList<T> mObservers = new ArrayList<T>();

为什么会这样？这是某种错误或已知限制吗？我该如何解决这个问题？ (不算 Robolectric，我决定停止使用它，因为它有自己的问题)

在任何人问之前；这仅在测试期间发生，经过测试的代码工作正常。

使用的版本:JUnit 4.12。 Mockito 1.10.19，支持库 25.0.0，Android Studio 2.2.2，jdk 1.8.0_112，

Answer 1

这可能是因为您尝试使用 JUnit 测试依赖于 Android 框架类的代码。

请阅读this answer到与完全相同的问题相关的另一个问题。