为什么会出现错误“method execute in android.os.AsyncTask not mocked”

Question

我正在编写一个Android应用程序，它需要监听UDP广播消息。

我试图在侦听器类中模拟AsyncTask，以便对其进行单元测试。

问题是我总是得到错误java.lang.RuntimeException：Method execute in android.os.AsyncTask not mocked。

public class DiscoveryListener
{
    WorkGroupEventHandler workGroupEventHandler;

    private AsyncTask<Void, Void, Void> asyncTask;
    private boolean listener_active = false;

    public boolean GetListener_active()
    {
        return listener_active;
    }

    public DiscoveryListener(WorkGroupEventHandler eventHandler)
    {
        workGroupEventHandler = eventHandler;
    }

    public void Start()
    {
        if (listener_active == false)
        {
            listener_active = true;
            RunUdpListener();
        }
    }

    public void Stop()
    {
        listener_active = false;
        asyncTask.cancel(true);
    }

    public void RunUdpListener()
    {
        asyncTask = new AsyncTask<Void, Void, Void>()
        {

        @Override
        protected Void doInBackground(Void... params)
        {
            byte[] msg = new byte[4096];
            DatagramPacket datagramPacket = new DatagramPacket(msg, msg.length);
            MulticastSocket multicastReceiveSocket = null;

            try
            {
                multicastReceiveSocket = new MulticastSocket( 60000 );

                while (listener_active)
                {
                    if (isCancelled() == false)
                    {
                        multicastReceiveSocket.receive(datagramPacket);
                        ProcessIncommingMessage(datagramPacket.getAddress(), msg);
                    }
                }
            }
            catch (Exception e)
            {
                e.printStackTrace();
            }
            finally
            {
                if (multicastReceiveSocket != null)
                {
                    multicastReceiveSocket.close();
                }
            }

            return null;
            }
        };

        asyncTask.execute();
    }
}


@RunWith(PowerMockRunner.class)
@PrepareForTest({android.util.Log.class, android.os.AsyncTask.class})
public class DiscoveryListenerUnitTest
{
    private WorkGroupEventHandler eventHandler = new WorkGroupEventHandler()
    {
        @Override
        public void onWorkGroupEventHandle(String IpAddress, String Workgroup, String SerialNumber)
        {
        }
    };

    private DiscoveryListener discoveryListener = new DiscoveryListener(eventHandler);
    private AsyncTask asyncTask;

    @Test
    public void discoveryListener_doesStart() throws Exception
    {
        PowerMockito.mockStatic(android.util.Log.class);

        PowerMockito.whenNew(AsyncTask.class).withNoArguments().thenReturn(asyncTask);
        asyncTask = PowerMockito.mock(AsyncTask.class);
        when(asyncTask.execute()).thenReturn(null);

        discoveryListener.Start();
        assertEquals(true, discoveryListener.GetListener_active());
    }
}

Answer 1

AsynctAsk.execute是最终的，而Mockito不能模拟最终的类或方法。

    Cannot mock final methods - their real behavior is executed without any exception. Mockito cannot warn you about mocking final methods so be vigilant.

具体地说，这是因为Java可以在编译时解析链接，这意味着Mockito不能使用其生成的子类和方法重写来改变行为。

您可以选择使用Powermock，它使用一个特殊的类加载器来重写旧的行为，或者使用Robolectric，它做同样的工作，但是用特定于Android的测试友好的替代实现（“shadows”）替换类，其中包括一个用于AsyncTask的实现。