How to mock Azure blobContainerClient.GetBlobsAsync() - azure

Question

I have a Azure blob container which I am accessing using below code -
var blobContainerClient = GetBlobContainer(containerName);
if (blobContainerClient != null)
{
// List all blobs in the container
await foreach (BlobItem blobItem in blobContainerClient.GetBlobsAsync())
{
queuedBlobsList.Add(new QueuedBlobs { BlobName = blobItem.Name, LastModified = blobItem.Properties.LastModified });
}
}
private BlobContainerClient GetBlobContainer(string containerName)
{
return gen2StorageClient != null
? gen2StorageClient.GetBlobContainerClient(containerName)
: gen1StorageClient.GetBlobContainerClient(containerName);
}
The clients are initialised in constructor -
public class BlobService : IBlobService
{
private readonly BlobServiceClient gen1StorageClient, gen2StorageClient;
public BlobService(BlobServiceClient defaultClient, IAzureClientFactory<BlobServiceClient> clientFactory)
{
gen1StorageClient = defaultClient;
if (clientFactory != null)
{
gen2StorageClient = clientFactory.CreateClient("StorageConnectionString");
}
}
}
And my unit test where I am setting GetBlobsAsync is like this -
But I want to add list of BlobItems to test another loop.
private static Mock<BlobContainerClient> GetBlobContainerClientMockWithListOfBlobs()
{
var blobContainerClientMock = new Mock<BlobContainerClient>("UseDevelopmentStorage=true", EnvironmentConstants.ParallelUploadContainer);
var cancellationToken = new CancellationToken();
var blobs = new List<BlobItem>();
//AsyncPageable<BlobItem> blobItems = new AsyncPageable<BlobItem>(); -- Not allowing
blobContainerClientMock.Setup(x => x.GetBlobsAsync(BlobTraits.All, BlobStates.All, null, cancellationToken)).Returns(It.IsAny<AsyncPageable<BlobItem>>());
return blobContainerClientMock;
}

Answer 1

I came to this question because I also had the same issue.
Based on this article
AsyncPageable<T> and Pageable<T> are classes that represent collections of models returned by the service in pages.
The method GetBlobsAsync returns an AsyncPageable.
To Create an AsyncPageable you need first to create a BlobItem Page.
To create a Page<T> instance, use the Page<T>.FromValues method, passing a list of items, a continuation token, and the Response.
So let's start creating the list of items:
var blobList = new BlobItem[]
{
BlobsModelFactory.BlobItem("Blob1"),
BlobsModelFactory.BlobItem("Blob2"),
BlobsModelFactory.BlobItem("Blob3")
};
Note: BlobItem has an internal constructor but I found in this answer that there's a BlobsModelFactory.
After having the list of blobs is time to create a Page<BlobItem>:
Page<BlobItem> page = Page<BlobItem>.FromValues(blobList, null, Mock.Of<Response>());
And finally, create the AsyncPageable<BlobItem>
AsyncPageable<BlobItem> pageableBlobList = AsyncPageable<BlobItem>.FromPages(new[] { page });
And now you are able to use this to mock GetBlobsAsync method:
blobContainerClientMock
.Setup(m => m.GetBlobsAsync(
It.IsAny<BlobTraits>(),
It.IsAny<BlobStates>(),
It.IsAny<string>(),
It.IsAny<CancellationToken>()))
.Returns(pageableBlobList);
I hope this helps others with this issue.
André