Question

I have a Mock challenge – I’m using MVC 3 with the nunit framework and trying to mock a controller has an HttpPostedFileBase as a parameter. The controller signature looks like this:

 public ActionResult UploadAttachment(AttachmentViewModel clientAttachment, HttpPostedFileBase file, string clientName)

I set up a Mock reference for my “file” parameter, but it complains that it will not take a Mock Object. I’m guessing that I need to set up a ControllerContext for this scenario, but I haven’t had any luck with that, either. For the first test I simply need the HttpPostedFileBase to return a null file (in the case that a blank file reference gets in). I have also read Scott Hanselman’s excellent article on this subject (computer Zen). It seems like the key sentence in the MVC section for my concern is “you’ll get a dynamically generated derived Mock of an HttpRequestBase while running outside a Webserver (like inside a test) when you’ve made your own ControllerContext.” That seems to be where I’m running into walls.

I know I need these elements:

controller.ControllerContext = new ControllerContext(mockContext.Object, new RouteData(), controller);
mockContext.SetupGet(c => c.Request).Returns(mockRequest.Object);
mockRequest.Setup(c => c.HttpMethod).Returns([not sure what to evoke here]);

I’m in the state of being stuck. Thank you for any advice or nudges in the right direction.

Answer 1

Assuming you use a real view model (which is used by your controller action, instead of using a gazillion of parameters):

public class MyViewModel
{
    public HttpPostedFileBase File { get; set; }

    // those won't be used in my example but you get the point
    public string ClientName { get; set; }
    public AttachmentViewModel ClientAttachment { get; set; }
}

and a controller with an action that you are trying to unit test:

public class HomeController : Controller
{
    [HttpPost]
    public ActionResult UploadAttachment(MyViewModel model)
    {
        if (!ModelState.IsValid)
        {
            return View(model);
        }

        var file = Path.Combine(Server.MapPath("~/App_Data"), model.File.FileName);
        model.File.SaveAs(file);
        return RedirectToAction("succes");
    }
}

you now have 2 cases to cover:

• invalid modelstate => a view is returned
• valid modelstate => the file is saved and we redirected.

Let’s get rolling:

[TestMethod]
public void UploadAttachment_Should_Return_View_If_ModelState_Is_Not_Valid()
{
    // arrange
    var sut = new HomeController();
    var model = new MyViewModel();
    sut.ModelState.AddModelError("file", "please select a file");

    // act
    var actual = sut.UploadAttachment(model);

    // assert
    Assert.IsInstanceOfType(actual, typeof(ViewResult));
}

and the second case of course:

[TestMethod]
public void UploadAttachment_Should_Save_File_If_Model_Is_Valid_And_Redirect()
{
    // arrange
    var sut = new HomeController();
    var file = new Mock<HttpPostedFileBase>();
    file.Setup(x => x.FileName).Returns("foo.txt");
    var model = new MyViewModel
    {
        File = file.Object
    };
    var server = new Mock<HttpServerUtilityBase>();
    server.Setup(x => x.MapPath("~/App_Data")).Returns(@"c:\wwwroot\App_Data");
    var httpContext = new Mock<HttpContextBase>();
    httpContext.Setup(x => x.Server).Returns(server.Object);
    sut.ControllerContext = new ControllerContext(httpContext.Object, new RouteData(), sut);

    // act
    var actual = sut.UploadAttachment(model);

    // assert
    Assert.IsInstanceOfType(actual, typeof(RedirectToRouteResult));
    file.Verify(x => x.SaveAs(@"c:\wwwroot\App_Data\foo.txt"));
}

Hope this will put you on the right track. Sorry it uses MSTest instead of NUnit but the port should be more than trivial (shouldn’t take you more than 30man-seconds of work). Replace [TestMethod] with [Test] and you should not be far from the target. And yeah, I bet 2¢ that this Assert.IsInstanceOfType has an equivalent in NUnit.