Unit test file upload to AWS S3

Question

What would be the best way to unit test if a file upload to a AWS S3 bucket succeeded?

Right now I am doing the following:

        [Test]
        public void UploadFileToAWS()
        {
            // Arrange
            var bucket = "bucketName";
            var keyName = "test_upload.txt";
            var originalFile = new FileStream(@"C:\test.txt", FileMode.Open, FileAccess.Read);

            // Act
            var aws = new AmazonWebServicesUtility(bucket);
            var awsUpload = aws.UploadFile(keyName,originalFile);

            // Assert
            Assert.AreEqual(true, awsUpload);
        }

The method UploadFile() is taken from the AWS documentation using a FileStream to upload to AWS.

What I do not like about this approach is, that it needs a local file (C:\test.txt) - so this unit test won't work if shared through version control.
How could I modify this unit test so it doesn't rely on a local file?

Would it make sense to use System.IO.Path.GetTempPath() to create a temporary text file that I upload and use as a comparison in the unit test?

I am fairly new to unit tests, so I am happy for any direction you can point me in :-)

Thank you very much!

Why can't you create your own `Stream` without relying on a file stream (e.g. http://stackoverflow.com/a/1879470/1663001)? That way you can download it and test it contains a known value too. — DavidG, Feb 22 '17 at 14:50
Great! That's exactly what I was looking for. Thank you DavidG :-) — jrn, Feb 22 '17 at 15:23

score 2 · Accepted Answer · edited May 23 '17 at 11:46

Instead of creating a stream from a file on your disk, use a MemoryStream instead. This way, the text you insert into it is a constant in your code and can also be used for downloading the file and testing the entire round trip process. So taking code from this answer:

private const string StringToTestWith = "some sort of test string goes in here";

[Test]
public void UploadFileToAWS()
{
    // Arrange
    var bucket = "bucketName";
    var keyName = "test_upload.txt";
    var uploadFile = GenerateStreamFromString(StringToTestWith);

    // Act
    var aws = new AmazonWebServicesUtility(bucket);
    var awsUpload = aws.UploadFile(keyName, uploadFile);

    // Assert
    Assert.AreEqual(true, awsUpload);
}

private static Stream GenerateStreamFromString(string s)
{
    var stream = new MemoryStream();
    var writer = new StreamWriter(stream);
    writer.Write(s);
    writer.Flush();
    stream.Position = 0;
    return stream;
}

And now you can write this test too:

[Test]
public void DoesDownloadGetTheCorrectValue()
{
    //This implementation is up to you
    var downloadedString = GetFileFromAWSSomehow();

    Assert.AreEqual(downloadedString, StringToTestWith);
}

Just for reference: If someone is looking for how to implement the `GetFileFromAWSSomehow()` method that @DavidG mentioned: [here is the AWS documention](http://docs.aws.amazon.com/AmazonS3/latest/dev/RetrievingObjectUsingNetSDK.html) on retrieving files from AWS. — jrn, Feb 22 '17 at 15:50

Unit test file upload to AWS S3

1 Answers1