Azure Blob 存储：模拟 CloudBlobContainer

Question

我正在尝试对一个将文件上传到 Azure Blob 存储的类进行单元测试。上传方法作为CloudBlobContainer输入。调用时_storageContainer.Object.GetBlockBlobReference()，会引发 System.NullReferenceException。谁能帮我嘲笑这个？

单元测试代码：

[TestClass()]
public class BlobStorageServiceUploadUnitTest
{
    private static BlobStorageService _service;
    private static Mock<CloudBlobContainer> _storageContainer;
    private static List<FileType> _extensions;
    private static int _maxSize;

    [ClassInitialize]
    public static void Setup_Service(TestContext context)
    {
        _extensions = new List<FileType> { FileType.Image };
        _maxSize = 2048;

        _storageContainer = new Mock<CloudBlobContainer>();

        _service = new BlobStorageService(new Mock<BEntitiesContainer>().Object, _storageContainer.Object);
    }

    [TestMethod()]
    public void When_FileIsDeleted()
    {
        var file = CreateMockFile("test.jpg", 500000);
        var blob = _storageContainer.Object.GetBlockBlobReference("deleteTest.jpg");
        blob.UploadFromStream(file.Object.InputStream);

        _service.DeleteFromStorage("deleteTest.jpg");

        var blobs = _storageContainer.Object.ListBlobs();
        Assert.AreEqual(0, blobs.Count());
    }


    public Mock<HttpPostedFileBase> CreateMockFile(string fileName, int sizeInBytes)
    {
        var file = new Mock<HttpPostedFileBase>();
        var stream = new MemoryStream();
        var bmp = new Bitmap(1, 1);
        var graphics = Graphics.FromImage(bmp);
        graphics.FillRectangle(Brushes.Black, 0, 0, 1, 1);
        bmp.Save(stream, ImageFormat.Jpeg);

        file.Setup(pf => pf.InputStream).Returns(stream);
        file.Setup(f => f.FileName).Returns(fileName);
        file.Setup(f => f.ContentLength).Returns(sizeInBytes);

        return file;
    }
}

测试类：

public class BlobStorageService : BaseRepository<User>
{
    private CloudBlobContainer _storageContainer;

    public BlobStorageService(BEntitiesContainer context, CloudBlobContainer storageContainer) : base(context)
    {
        Context = context;
        _storageContainer = storageContainer;
    }

    public void DeleteFromStorage(string fileName)
    {
        _storageContainer.GetBlockBlobReference(fileName).DeleteIfExists();
    }
}

Answer 1

您唯一能做的一件事就是将 CloudBlobContainer 操作移动到具有抽象实现的单独服务中。在这种情况下，您将能够模拟该服务，而根本不需要接触 Azure 类。

例如：

public interface IAzureServiceWrapper
{
    CloudBlockBlob GetBlockBlobReference(CloudBlobContainer storageContainer, string fileName);
}

public class AzureServiceWrapper : IAzureServiceWrapper
{
    public CloudBlockBlob GetBlockBlobReference(CloudBlobContainer storageContainer, string fileName)
    {
         storageContainer.GetBlockBlobReference(fileName).DeleteIfExists();
    }
}

在这种情况下，模拟 AzureServiceWrapper 将非常容易，并且此解决方案将解决单元测试中使用的 Azure 类的所有问题。您只需在 BlobStorageService 中使用 AzureServiceWrapper 而不是 CloudBlobContainer 即可。