public async Task DownFileAsync_CloudBlobGiven_DownloadsFile()
{
string blobName = NewRandomString();
string filecontents = NewRandomString();
_cloudBlob.Setup(_ => _.DownloadToStreamAsync(It.IsAny <Stream>()))
.Verifiable();
Stream stream = await _blobClient.DownloadToStreamAsync(_cloudBlob.Object);
stream.Position.Should().Be(0);
}