Question

I have a fairly simple class that I’m trying to unit test. I’m very new to unit testing in general, and I’m not sure what I should be testing here.

The only test case that I can figure out how to code is a null argument of stream. Besides that, I’m not sure how to test the results of a PutObjectRequest or what else. If I should be using mocks here, how?

public class AmazonS3Service : IAmazonS3Service
{
    private readonly Uri baseImageUrl;
    private readonly Uri s3BaseUrl;
    private readonly string imageBucket;

    public AmazonS3Service()
    {
        imageBucket = ConfigurationManager.AppSettings["S3.Buckets.Images"];

        s3BaseUrl = new Uri(ConfigurationManager.AppSettings["S3.BaseAddress"]);
        baseImageUrl = new Uri(s3BaseUrl, imageBucket);
    }

    public Image UploadImage(Stream stream)
    {
        if (stream == null) throw new ArgumentNullException("stream");
        var key = string.Format("{0}.jpg", Guid.NewGuid());

        var request = new PutObjectRequest
        {
            CannedACL = S3CannedACL.PublicRead,
            Timeout = -1,
            ReadWriteTimeout = 600000, // 10 minutes * 60 seconds * 1000 milliseconds
            InputStream = stream,
            BucketName = imageBucket,
            Key = key
        };

        using (var client = new AmazonS3Client())
        {
            using (client.PutObject(request))
            {
            }
        }

        return new Image
        {
            UriString = Path.Combine(baseImageUrl.AbsoluteUri, key)
        };
    }
}

Answer 1

Things I would look at:

• Mock your configuration manager to return invalid data for the bucket and the URL. (null, invalid urls, invalid buckets)

• Does S3 support https ? If so mock it, if not, mock it and verify you get a valid error.

• Pass different kinds of streams in (Memory, File, other types).

• Pass in streams in different states (Empty streams, streams that have been read to the
  end, …)

• I would allow the timeouts to be set as parameters, so you can test with really low
  timeouts and see what errors you get back.

• I would also test with duplicate keys, just to verify the error message. Even though you are using guids, you are storing to an amazon server where someone else could use the S3 API to store documents and could theoretically create a file that appears to be a guid, but could create a conflict down the road (unlikely, but possible)