I am using xUnit and Moq for writing test cases. I am using the code below to create a Mock but am getting the highlighted issue.

CloudBlockBlob source = null;
AccessCondition sourceAccessCondition = null;
AccessCondition destAccessCondition = null;
BlobRequestOptions options = null;
OperationContext operationContext = null;
CloudBlobContainer container = new CloudBlobContainer(uri);
Task task = null;
DeleteSnapshotOption deleteSnapshotOption = new DeleteSnapshotOption();

var mockCloudBlobClient = new Mock<Microsoft.WindowsAzure.Storage.Blob.CloudBlobClient>();
mockCloudBlobClient.Setup(repo => repo.GetContainerReference("sample")).Returns(container);

var mockCloudBlobContainer = new Mock<Microsoft.WindowsAzure.Storage.Blob.CloudBlobContainer>(uri);
mockCloudBlobContainer.Setup(repo => repo.GetBlockBlobReference("sample")).Returns(new CloudBlockBlob(uri));

var mockBlobServiceProvider = new Mock<BlobServiceProvider>();
mockBlobServiceProvider.Setup(repo => repo.GetBlockBlobContainer("sample")).Returns(new CloudBloblContainer(new Uri("http://mytest")));

The line mockBlobServiceProvider.Setup(repo => repo.GetBlockBlobContainer("sample")).Returns(new CloudBloblContainer(new Uri("http://mytest"))); is giving me this error:

System.NotSupportedException: 'Unsupported expression: repo => repo.GetBlockBlobContainer("sample")

Non-overridable members (here: BlobServiceProvider.GetBlockBlobContainer) may not be used in setup / verification expressions.'

Class BlobServiceProvider:

Public Class BlobServiceProvider
{
    public CloudBlobContainer GetBlockBlobContainer(string containerName)
    {
        CloudBlobContainer Container = blobClient.GetContainerReference(containerName);
        Container.CreateIfNotExistsAsync();
        return Container;
    }
}

How can I resolve this issue?