c# - 使用 AutoFac 和 AutoMock 模拟 CloudBlobClient

Question

我正在尝试为我的 AzureBlobRepository 编写单元测试。存储库在构造函数中接收一个 CloubBlobClient。我想模拟客户端，但这给出了一个异常(exception):

using (var mock = AutoMock.GetLoose())
{
    var mockClient = mock.Mock<CloudBlobClient>();
}

Cannot choose between multiple constructors with equal length 2 on type 'Microsoft.WindowsAzure.Storage.Blob.CloudBlobClient'. Select the constructor explicitly, with the UsingConstructor() configuration method, when the component is registered.

当然，在我的单元测试中我没有注册任何东西，所以这条消息不是很有帮助。

我还尝试了其他方法，例如提供 NameParameters、TypedParameters，或调用 mock.Create 代替 mock.Mock，但我尝试的所有方法都返回相同的异常消息。

(在CloudBlobContainer上也出现了同样的问题)

实现接口(interface)后更新 这是我编写的单元测试示例:

[TestMethod]
public void AzureBlobRepository_GetByIdAsync_ReturnsContent()
{    
    Guid blobId = Guid.NewGuid();
    Guid directoryName = Guid.NewGuid();
    string containerName = "unittest";

    using (var mock = AutoMock.GetLoose())
    {
        var mockClient = mock.Mock<ICloudBlobClient>();
        var mockContainer = mock.Mock<ICloudBlobContainer>();
        var mockDirectory = mock.Mock<ICloudBlobDirectory>();
        // notice that we're not using AutoMock here, it fails to create the mock
        var mockBlob = new Mock<CloudBlockBlob>(new Uri($"http://tempuri.org/{containerName}/{directoryName}/{blobId}"));
        mockBlob.Setup(m => m.DownloadTextAsync()).Returns(Task.FromResult("content"));

        mockClient.Setup(m => m.GetContainerReference(containerName))
            .Returns(mockContainer.Object);
        mockContainer.Setup(m => m.GetDirectoryReference(directoryName.ToString()))
            .Returns(mockDirectory.Object);
        mockDirectory.Setup(m => m.GetBlockBlobReference(blobId.ToString()))
            .Returns(mockBlob.Object);

        var repository = mock.Create<AzureBlobRepository>(
            new TypedParameter(typeof(ICloudBlobClient), mockClient.Object),
            new NamedParameter("container", containerName),
            new NamedParameter("directory", directoryName));

        var result = repository.GetByIdAsync(blobId, directoryName).Result;
        result.ShouldBe("content");
    }
}

Answer 1

这些类应被视为第 3 方实现问题。这意味着您无法控制它们，我们不应该 mock 我们无法控制的东西。它们应该封装在您可以控制的抽象之后，并且可以在单独测试时根据需要进行模拟。

public interface ICloudBlobClient {
    //...expose only the functionality I need
}

public class CloudBlobClientWrapper : ICloudBlobClient {
    private readonly CloudBlobClient client;

    public CloudBlobClientWrapper(CloudBlobClient client) {
        this.client = client;
    }

    //...implement interface wrapping
}

正是出于这个原因，类应该依赖于抽象而不是具体化。模拟具体类往往会产生链式 react

包装器不需要完全包装客户端，但可以聚合功能以免暴露实现问题。

所以现在当单独测试时你可以模拟你控制的抽象

using (var mock = AutoMock.GetLoose()) {
    var mockClient = mock.Mock<ICloudBlobClient>();

    /// ...and the rest of the test.
}