Question

我正在使用Moq为C＃应用程序编写测试。我的测试初始化程序包含以下代码：

UnityContainer unityContainer = new UnityContainer();

_serviceMock = new Mock<IService>();
_serviceMock.Setup(mock => mock.GetSearchInfoAsync(It.IsAny<CancellationToken>(), It.IsAny<IEnumerable<string>>(), It.IsAny<identifierType>(), It.IsAny<bool>())).Callback(() => _count++);
unityContainer.RegisterInstance(typeof(IService), _serviceMock.Object, new ContainerControlledLifetimeManager());

我想测试一次调用。我这样想：

int _count = 0;

[TestMethod]
public void Properties_Test()
{
    _serviceMock.Verify(mock => mock.GetSearchInfoAsync(It.IsAny<CancellationToken>(), It.IsAny<IEnumerable<string>>(), It.IsAny<identifierType>(), It.IsAny<bool>()), Times.Exactly(1), "Invocation was performed " + _count + " times but was expected only once!");
}

这是实际被调用的方法：

private void Search(string queryValue, identifierType identifierType)
{
    CancellationToken cancellationToken;

    lock (_syncLock)
    {
        _cancellationTokenSource.Cancel();
        _cancellationTokenSource = new CancellationTokenSource();
        cancellationToken = _cancellationTokenSource.Token;
    }

    IService Service = ServiceLocator.Current.GetInstance<IService>();

    Service.GetSearchInfoAsync(cancellationToken, new[] {queryValue}, identifierType)
        .ContinueWith(
            task =>
            {
                // Do stuff
            }, CancellationToken.None, TaskContinuationOptions.None, TaskScheduler.Default);
}

问题是，如果我使用上面详述的这一行，

_serviceMock.Setup(mock => mock.GetSearchInfoAsync(It.IsAny<CancellationToken>(), It.IsAny<IEnumerable<string>>(), It.IsAny<identifierType>(), It.IsAny<bool>())).Callback(() => _count++);

返回null并生成NullPointerException：

Service.GetSearchInfoAsync(cancellationToken, new[] {queryValue}, identifierType)

但是，如果我注释掉该行，则测试运行正常（尽管不计算调用次数）。

我做错了什么？这是我第一次使用Moq，据我所知，我已正确实现了计数功能。

编辑：根据Chris Sinclair的建议，我已将初始化更改为此，这解决了问题：

UnityContainer unityContainer = new UnityContainer();

_serviceMock = new Mock<IService>();
Task<IEnumerable<ISearchResult>> task = new Task<IEnumerable<ISearchResult>>(Enumerable.Empty<ISearchResult>);
_serviceMock.Setup(mock => mock.GetSearchInfoAsync(It.IsAny<CancellationToken>(), It.IsAny<IEnumerable<string>>(), It.IsAny<identifierType>(), It.IsAny<bool>())).Returns(task).Callback(() => _count++);
unityContainer.RegisterInstance(typeof(IService), _serviceMock.Object, new ContainerControlledLifetimeManager());

Answer 1

当你＆＃34;设置＆＃34;方法，您设置回调但不提供返回值。因此，当调用mocked方法时，它将返回返回类型的默认值（在这种情况下，Task<>类型将导致null返回值）。因此，当您的Search方法调用您的模拟GetSearchInfoAsync方法时，它会收到null引用，该引用在以后尝试在其上调用.ContinueWith时自然会失败。

尝试添加.Returns()，将虚拟Task<>提供给您的模拟方法：

_serviceMock.Setup(mock => mock.GetSearchInfoAsync(It.IsAny<CancellationToken>(), It.IsAny<IEnumerable<string>>(), It.IsAny<identifierType>(), It.IsAny<bool>()))
    .Returns(new Task<IEnumerable<ISearchResult>>(Enumerable.Empty<ISearchResult>))
    .Callback(() => _count++);

如果使用安装程序，Moq模拟调用返回null

1 个答案: