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);
        }