Android RecyclerView 适配器项目计数在单元测试中返回 0

Question

我正在尝试使用 AndroidJunit4 测试 RecyclerView，这是我的测试代码：

@Rule
    public ActivityTestRule<ProductListActivity> rule  = new  ActivityTestRule<>(ProductListActivity.class);

............................
..........................

@Test
    public void ensureDataIsLoadingOnSuccess() throws Exception {
        ProductListActivity activity = rule.getActivity();
        ...........................
        ............

        activity.runOnUiThread(new Runnable() {
        public void run() {
            activity.displayProducts(asList(product1, product2), 0);
        }
    });

        assertEquals(2, mAdapter.getItemCount());
        assertThat(((ProductAdapter) mAdapter).getItemAtPosition(0),sameInstance(product1));
        assertThat(((ProductAdapter) mAdapter).getItemAtPosition(1),sameInstance(product2));


    }

这是我在 Activity 中的 displayProducts() 代码：

@Override
    public void displayProducts(List<Product> products, Integer pageNo) {
        progressBar.setVisibility(View.GONE);
        if (pageNo == 0 && products.size() == 0) {
            noProductTextView.setVisibility(View.VISIBLE);
        } else {
            mProductAdapter.addProduct(products);
            noProductTextView.setVisibility(View.GONE);
            productListView.setVisibility(View.VISIBLE);
        }
    }

它给出的错误如下：

junit.framework.AssertionFailedError: expected:<2> but was:<0>
at junit.framework.Assert.fail(Assert.java:50)
at junit.framework.Assert.failNotEquals(Assert.java:287)
at junit.framework.Assert.assertEquals(Assert.java:67)
at junit.framework.Assert.assertEquals(Assert.java:199)
at junit.framework.Assert.assertEquals(Assert.java:205)
at com.kaushik.myredmart.ui.ProductListActivityTest.ensureDataIsLoadingOnSuccess(ProductListActivityTest.java:94)

请帮忙看看我的代码有什么问题？

Answer 1

原因是您的 Espresso 测试没有等待您的加载任务，这很耗时。 您需要使用espresso-idling-resource 告诉它等待此任务完成。

然后你需要一个类来实现IdlingResource 并将它声明为你的Activity。

当您的 Espresso 测试运行时，它会知道并等待您的耗时任务完成并测试结果。

首先，添加它的依赖。

 compile "com.android.support.test.espresso:espresso-idling-resource:2.2.2"

其次，您需要文件夹 src/main/java/your-package 中的两个 Java 文件。
SimpleCountingIdlingResource.java

public final class SimpleCountingIdlingResource implements IdlingResource {

  private final String mResourceName;

  private final AtomicInteger counter = new AtomicInteger(0);

  // written from main thread, read from any thread.
  private volatile ResourceCallback resourceCallback;

  /**
   * Creates a SimpleCountingIdlingResource
   *
   * @param resourceName the resource name this resource should report to Espresso.
   */
  public SimpleCountingIdlingResource(String resourceName) {
    mResourceName = checkNotNull(resourceName);
  }

  @Override public String getName() {
    return mResourceName;
  }

  @Override public boolean isIdleNow() {
    return counter.get() == 0;
  }

  @Override public void registerIdleTransitionCallback(ResourceCallback resourceCallback) {
    this.resourceCallback = resourceCallback;
  }

  /**
   * Increments the count of in-flight transactions to the resource being monitored.
   */
  public void increment() {
    counter.getAndIncrement();
  }

  /**
   * Decrements the count of in-flight transactions to the resource being monitored.
   *
   * If this operation results in the counter falling below 0 - an exception is raised.
   *
   * @throws IllegalStateException if the counter is below 0.
   */
  public void decrement() {
    int counterVal = counter.decrementAndGet();
    if (counterVal == 0) {
      // we've gone from non-zero to zero. That means we're idle now! Tell espresso.
      if (null != resourceCallback) {
        resourceCallback.onTransitionToIdle();
      }
    }

    if (counterVal < 0) {
      throw new IllegalArgumentException("Counter has been corrupted!");
    }
  }
}

EspressoIdlingResource.java

public class EspressoIdlingResource {

  private static final String RESOURCE = "GLOBAL";

  private static SimpleCountingIdlingResource mCountingIdlingResource =
      new SimpleCountingIdlingResource(RESOURCE);

  public static void increment() {
    mCountingIdlingResource.increment();
  }

  public static void decrement() {
    mCountingIdlingResource.decrement();
  }

  public static IdlingResource getIdlingResource() {
    return mCountingIdlingResource;
  }
}

好的。让我们转到您有一项耗时任务的活动。 首先，将此方法放在底部。

@VisibleForTesting
    public IdlingResource getCountingIdlingResource() {
        return EspressoIdlingResource.getIdlingResource();
    }

在您耗时的任务中。你应该告诉你的 Espresso 像这样等待。

EspressoIdlingResource.increment();

  yourTask.run(new Callback() {
    void onFinish(){
      EspressoIdlingResource.decrement();
    }
  })

最后一步是在您的 UI 测试类中定义这些方法。

@Before
public void registerIdlingResource() {
    Espresso.registerIdlingResources(mOnBoardActivityTestRule.getActivity().getCountingIdlingResource());
}

/**
 * Unregisters your idling resource so it can be garbage collected and does not leak any memory
 */
@After
public void unregisterIdlingResource() {
    Espresso.unregisterIdlingResources(mOnBoardActivityTestRule.getActivity().getCountingIdlingResource());
}

是的。终于完成了。

Answer 2

我可以在这里看到一个问题，您在 Main/UI 线程能够更新它之前查询列表大小。因此，您必须在当前线程中等待，直到 Activity 完成更新主线程上的列表。

你可以的，

Thread.sleep(500);

在Test类中等待，在Activity中测试list设置行为，你会发现断言是有效的。

由于主线程无限运行直到应用程序运行，您必须实现 Activity 提供的回调接口，以便在填充列表完成时收到通知。