asp.net mvc - Mocking HttpPostedFileBase and InputStream for unit-test

Question

I want to test the following line of code:

...
Bitmap uploadedPicture = Bitmap.FromStream(model.Picture.InputStream) as Bitmap;
...

Picture is a property in my model type HttpPostedFileBase. So I would like to mock a HttpPostedFileBase property for unit-testing:

model.Picture = new Mock<HttpPostedFileBase>().Object;

No problem at all.

Now I have to mock the InputStream, otherwise it's null:

model.Picture.InputStream = new Mock<Stream>().Object;

This isn't working as the InputStream is read-only (hasn't a setter method):

public virtual Stream InputStream { get; }

Is there a good and clean way to handle this problem? One solution would be to override HttpPostedFileBase in a derived class for my unit-test. Any other idea?

Answer 1

Hi there :) I did something like,

    [TestInitialize]
    public void SetUp()
    {
        _stream = new FileStream(string.Format(
                        ConfigurationManager.AppSettings["File"],
                        AppDomain.CurrentDomain.BaseDirectory), 
                     FileMode.Open);

        // Other stuff
    }

And on the Test itself,

    [TestMethod]
    public void FileUploadTest() 
    {
        // Other stuff

        #region Mock HttpPostedFileBase

        var context = new Mock<HttpContextBase>();
        var request = new Mock<HttpRequestBase>();
        var files = new Mock<HttpFileCollectionBase>();
        var file = new Mock<HttpPostedFileBase>();
        context.Setup(x => x.Request).Returns(request.Object);

        files.Setup(x => x.Count).Returns(1);

        // The required properties from my Controller side
        file.Setup(x => x.InputStream).Returns(_stream);
        file.Setup(x => x.ContentLength).Returns((int)_stream.Length);
        file.Setup(x => x.FileName).Returns(_stream.Name);

        files.Setup(x => x.Get(0).InputStream).Returns(file.Object.InputStream);
        request.Setup(x => x.Files).Returns(files.Object);
        request.Setup(x => x.Files[0]).Returns(file.Object);

        _controller.ControllerContext = new ControllerContext(
                                 context.Object, new RouteData(), _controller);

        // The rest...
    }

Hope this can provide an idea to your solution :)