Mock BlobResultSegment

In #335 this class is not sealed anymore, but I still have a hard time mocking this class with Moq as the constructor is internal and results in an exception.

System.NotSupportedException : Parent does not have a default constructor. The default constructor must be explicitly defined.

I tried to go with reflection, but fieldInfo is always null.

var segment = System.Runtime.Serialization.FormatterServices.GetUninitializedObject(typeof(BlobResultSegment));
var fieldInfo = typeof(BlobResultSegment).GetField(@"Results");

I even tried to GetFields with a lot BindingFlags, but then I only got the private backing fields and not the public fields.

BindingFlags flags = BindingFlags.Public | BindingFlags.NonPublic |
                         BindingFlags.Static | BindingFlags.Instance |
                         BindingFlags.DeclaredOnly;

The goal to unseal the class was to be able to mock it. What is the best solution to mock this class?

My not so pretty work around is as follows:

private BlobResultSegment CreateResultSegment(CloudBlockBlob blob)
        {
            BindingFlags flags = BindingFlags.Public | BindingFlags.NonPublic |
                         BindingFlags.Static | BindingFlags.Instance |
                         BindingFlags.DeclaredOnly;

            var segment = System.Runtime.Serialization.FormatterServices.GetUninitializedObject(typeof(BlobResultSegment));
            var fields = segment.GetType().GetFields(flags);
            var fieldInfo = fields.First(f => f.Name.Contains(@"Results"));

            fieldInfo.SetValue(segment, new[] { blob });
            return (BlobResultSegment)segment;
        }

[erezvani1529]

Thanks @tverboon, @PureKrome

Thanks for sharing the information and the workaround for the issue (which seems to be the only working one).

As mentioned in #465, we are discussing improvements to increase mock-ability of our library(by either virtualizing the properties and adding default constructors or adding interfaces for the types). These changes once pinned down, will be included in our next breaking change release(9.0) and we will announce the final decision on this. Shall we use #465 to track this task and close the related ones such as this issue?

Thanks, Elham

[PureKrome]

@tverboon out of interest, can you provide some code to how you use a BobResultSegment in some normal code (not mocks, etc)

I would like to see how it’s used, to then understand how it could be mocked (regardless if the mocking doesn’t work, currently). This way, we can help show the MS Team how we are using their code and suggest how/what should be fixed.

Example reference to another Issue re: mocked => https://github.com/Azure/azure-storage-net/issues/465