模拟使用最小起订量的异步回调的方法

Question

我正在对一些异步代码进行单元测试。我试图将其抽象化以使问题更清楚。我的问题是我想设置模拟 Bar 以在 BeginWork returns 之后执行 Foo 的私有回调方法。回调应该在 ManualResetEvent 上调用 Set()，允许调用线程继续到运行。当我运行测试时，我的线程在调用 WaitOne().

时无限期阻塞

被测代码：

using System.Threading;
using NUnit.Framework;
using Moq;
using System.Reflection;

public interface IBar
{
    int BeginWork(AsyncCallback callback);
}

public class Bar : IBar
{
    public int BeginWork(AsyncCallback callback)
    {
        // do stuff
    }   // execute callback
}

public class Foo
{
    public static ManualResetEvent workDone = new ManualResetEvent(false);
    private IBar bar;

    public Foo(IBar bar)
    {
        this.bar = bar;
    }

    public bool DoWork()
    {
        bar.BeginWork(new AsyncCallback(DoWorkCallback));
        workDone.WaitOne(); // thread blocks here
        return true;
    }

    private void DoWorkCallback(int valueFromBeginWork)
    {
        workDone.Set();
    }
}

测试代码：

[Test]
public void Test()
{
    Mock<IBar> mockBar = new Mock<IBar>(MockBehavior.Strict);

    // get private callback
    MethodInfo callback = typeof(Foo).GetMethod("DoWorkCallback", 
                  BindingFlags.Instance | BindingFlags.NonPublic);

    mockBar.Setup(() => BeginWork(It.IsAny<AsyncCallback>())) 
                        .Returns(0).Callback(() => callback.Invoke(0));

    Foo = new Foo(mockBar.Object);
    Assert.That(Foo.DoWork());
}

Answer 1

首先观察到您在 state 中传递了一个模拟的 ISocket 并尝试在异步回调中将其转换为 Socket 这将导致空错误，这意味着 connectDone.Set() 永远不会被调用，所以 WaitOne 不会解锁。

将其更改为

private void ConnectCallback(IAsyncResult result) {
    ISocket client = (ISocket)result.AsyncState;
    client.EndConnect(result);
    connectDone.Set();
}

第二个观察是您没有正确设置模拟调用。这里不需要反射，因为您需要从模拟中获取传递的参数，然后在模拟回调设置中调用

以下内容基于您的原始代码。查看它以了解上面解释的内容。

[TestClass]
public class SocketManagerTests {
    [TestMethod]
    public void ConnectTest() {
        //Arrange
        var mockSocket = new Mock<ISocket>();
        //async result needed for callback
        IAsyncResult mockedIAsyncResult = Mock.Of<IAsyncResult>();
        //set mock
        mockSocket.Setup(_ => _.BeginConnect(
                It.IsAny<EndPoint>(), It.IsAny<AsyncCallback>(), It.IsAny<object>())
            )
            .Returns(mockedIAsyncResult)
            .Callback((EndPoint ep, AsyncCallback cb, object state) => {
                var m = Mock.Get(mockedIAsyncResult);
                //setup state object on mocked async result
                m.Setup(_ => _.AsyncState).Returns(state);
                //invoke provided async callback delegate
                cb(mockedIAsyncResult);
            });

        var manager = new SocketManager(mockSocket.Object);

        //Act
        var actual = manager.Connect();

        //Assert
        Assert.IsTrue(actual);
        mockSocket.Verify(_ => _.EndConnect(mockedIAsyncResult), Times.Once);
    }
}

最后，我认为您应该考虑更改此代码以使用 TPL 来绕过整个回调和 IAsyncResult 戏剧。基本上公开异步 API 并用 TaskCompletionSource<T> 包装调用，但我想这超出了这个问题的范围。

模拟使用最小起订量的异步回调的方法

Mocking a method that uses an asynchronous callback with moq

c#

unit-testing

nunit

moq

iasyncresult