Render a View during a Unit Test - ControllerContext.DisplayMode

Question

I am working on an ASP.NET MVC 4 web application that generates large and complicated reports. I want to write Unit Tests that render a View in order to make sure the View doesn't blow up depending on the Model:

 [Test]
 public void ExampleTest(){                  
     var reportModel = new ReportModel();

     var reportHtml = RenderRazorView(
           @"..\..\Report.Mvc\Views\Report\Index.cshtml", 
           reportModel);

     Assert.IsFalse(
         string.IsNullOrEmpty(reportHtml),
         "View Failed to Render!");          
 }

 public string RenderRazorView(string viewPath, object model){
    //WHAT GOES HERE?
 }

I have seen a lot of information about this around the web, but it's either arguing against testing vies, or can only be used in the context of a web request.

• Arguing Against - Unit Testing the Views? - This concludes there should be no logic in the View so you should only need to test compilation. I think there is value in testing the View to make sure there aren't Null Reference Exceptions, the correct sections are shown, etc.
• Context of a Web Request - Render a view as a string - This is to render a View to be sent in an email. But this approach requires being called via a web request (ie a valid HttpContextBase).

I have been working to adapt Render a view as a string to work with a Mocked HttpContextBase, but have been running into problems when using a Mocked ControllerContext:

Object reference not set to an instance of an object. at System.Web.WebPages.DisplayModeProvider.GetDisplayMode(HttpContextBase context) at System.Web.Mvc.ControllerContext.get_DisplayMode() at System.Web.Mvc.VirtualPathProviderViewEngine.GetPath(ControllerContext controllerContext, String[] locations, String[] areaLocations, String locationsPropertyName, String name, String controllerName, String cacheKeyPrefix, Boolean useCache, String[]& searchedLocations)

This is the code I have so far:

    public string RenderRazorView(string viewPath, object model)
    {
        var controller = GetMockedDummyController();

        //Exception here
        var viewResult = 
            ViewEngines.Engines.FindView(controller.ControllerContext, "Index", "");

        using (var sw = new StringWriter())
        {
            var viewContext =
                new ViewContext(
                    controller.ControllerContext,
                    viewResult.View,
                    new ViewDataDictionary(model),
                    new TempDataDictionary(),
                    sw);

            viewResult.View.Render(viewContext, sw);

            return sw.ToString();
        }
    }

I'm building the Controller:

    private Controller GetMockedDummyController()
    {
        var HttpContextBaseMock = new Mock<HttpContextBase>();
        var HttpRequestMock = new Mock<HttpRequestBase>();
        var HttpResponseMock = new Mock<HttpResponseBase>();
        HttpContextBaseMock.SetupGet(x => x.Request).Returns(HttpRequestMock.Object);
        HttpContextBaseMock.SetupGet(x => x.Response).Returns(HttpResponseMock.Object);

        var controller = new DummyController();

        var routeData = new RouteData();
        routeData.Values.Add("controller", "Dummy");

        controller.ControllerContext = 
            new ControllerContext(
                HttpContextBaseMock.Object,
                routeData,
                controller);

        controller.Url =
            new UrlHelper(
                new RequestContext(
                    HttpContextBaseMock.Object,
                    routeData), 
                new RouteCollection());

        return controller;
    }

The DummyController is just public class DummyController : Controller {}

Question

Give the path to a View, how can I render it to HTML from a Test project? Or more specifically, how can I mock out the ControllerContext.DisplayMode?

Answer 1

Assuming you have complete separation of concerns, is it necessary to instantiate the controller at all? If not, then perhaps you can use RazorEngine to test your views.

var contents = File.ReadAllText("pathToView"); 
var result = Razor.Parse(contents,model);
// assert here