Unit testing method converting MVC view to string using View.Render method

Question

I have written method that converts MVC view to string and test method to check if it returns string.

Of course it works with Web but when I run test in NUnit it throws a NullReferenceException in System.Web when method tries to call View.Render.

Here is StackTrace:

   w System.Web.VirtualPath.GetCacheKey()
   w System.Web.Compilation.BuildManager.GetCacheKeyFromVirtualPath(VirtualPath virtualPath, Boolean& keyFromVPP)
   w System.Web.Compilation.BuildManager.GetVPathBuildResultFromCacheInternal(VirtualPath virtualPath, Boolean ensureIsUpToDate)
   w System.Web.Compilation.BuildManager.GetVPathBuildResultInternal(VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile, Boolean throwIfNotFound, Boolean ensureIsUpToDate)
   w System.Web.Compilation.BuildManager.GetVPathBuildResultWithNoAssert(HttpContext context, VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile, Boolean throwIfNotFound, Boolean ensureIsUpToDate)
   w System.Web.Compilation.BuildManager.GetVirtualPathObjectFactory(VirtualPath virtualPath, HttpContext context, Boolean allowCrossApp, Boolean throwIfNotFound)
   w System.Web.Compilation.BuildManager.GetObjectFactory(String virtualPath, Boolean throwIfNotFound)
   w System.Web.Mvc.BuildManagerWrapper.System.Web.Mvc.IBuildManager.FileExists(String virtualPath)
   w System.Web.Mvc.BuildManagerViewEngine.FileExists(ControllerContext controllerContext, String virtualPath)
   w System.Web.Mvc.VirtualPathProviderViewEngine.GetPathFromSpecificName(ControllerContext controllerContext, String name, String cacheKey, String[]& searchedLocations)
   w System.Web.Mvc.VirtualPathProviderViewEngine.GetPath(ControllerContext controllerContext, String[] locations, String[] areaLocations, String locationsPropertyName, String name, String controllerName, String cacheKeyPrefix, Boolean useCache, String[]& searchedLocations)
   w System.Web.Mvc.VirtualPathProviderViewEngine.FindView(ControllerContext controllerContext, String viewName, String masterName, Boolean useCache)
   w System.Web.Mvc.ViewEngineCollection.<>c__DisplayClassc.<FindView>b__b(IViewEngine e)
   w System.Web.Mvc.ViewEngineCollection.Find(Func`2 lookup, Boolean trackSearchedPaths)
   w System.Web.Mvc.ViewEngineCollection.Find(Func`2 cacheLocator, Func`2 locator)
   w System.Web.Mvc.ViewEngineCollection.FindView(ControllerContext controllerContext, String viewName, String masterName)
   w MvcApplication.Infrastructure.Services.MailingService.RenderEmailBody[T](String viewPath, T model, ControllerContext controllerContext, Boolean isParialView) w d:\MyProjects\CertyfikatyNoble\branches\Certyfikaty3\MvcApplication\Infrastructure\Services\MailingService.cs:wiersz 175
   w MvcApplication.Tests.MailingServiceTests.ViewToStrngTest() w d:\MyProjects\CertyfikatyNoble\branches\Certyfikaty3\MvcApplication.Tests\MailingServiceTests.cs:wiersz 144

Rendering method code:

public string RenderEmailBody<T>(string viewPath, T model, ControllerContext controllerContext, bool isParialView)
{
    ViewEngineResult viewEngineResult = null;
    if (isParialView == true)
    {
        viewEngineResult = ViewEngines.Engines.FindPartialView(controllerContext, viewPath);
    }
    else
    {
        viewEngineResult = ViewEngines.Engines.FindView(controllerContext, viewPath, null);
    }

    if (viewEngineResult == null)
    {
        throw new FileNotFoundException("Coukld not find view.");
    }

    var view = viewEngineResult.View;
    controllerContext.Controller.ViewData.Model = model;

    string result = null;

    using (var sw = new StringWriter())
    {
        var ctx = new ViewContext(controllerContext, view,
                                    controllerContext.Controller.ViewData,
                                    controllerContext.Controller.TempData,
                                    sw);
        view.Render(ctx, sw);
        result = sw.ToString();
    }

    return result;
}

And test method with controller context mock:

Mock<HttpBrowserCapabilitiesBase> browserMock = new Mock<HttpBrowserCapabilitiesBase>();
browserMock.Setup(m => m.IsMobileDevice).Returns(false);

Mock<HttpServerUtilityBase> httpServerUtilityBaseMock = new Mock<HttpServerUtilityBase>(MockBehavior.Strict);

Mock<HttpResponseBase> httpResponseMock = new Mock<HttpResponseBase>(MockBehavior.Strict);
httpResponseMock.Setup(m => m.Cookies).Returns(new HttpCookieCollection() { new HttpCookie("ResponseCookieTest") });

Mock<HttpRequestBase> httpRequestMock = new Mock<HttpRequestBase>(MockBehavior.Strict);
httpRequestMock.Setup(m => m.UserHostAddress).Returns("127.0.0.1");
httpRequestMock.Setup(m => m.Cookies).Returns(new HttpCookieCollection() { new HttpCookie("RequestCookieTest") });
httpRequestMock.Setup(m => m.UserAgent).Returns("None");
httpRequestMock.Setup(m => m.Browser).Returns(browserMock.Object);
httpRequestMock.Setup(m => m.ApplicationPath).Returns("/");
httpRequestMock.Setup(m => m.AppRelativeCurrentExecutionFilePath).Returns("/");
httpRequestMock.Setup(m => m.PathInfo).Returns(string.Empty);
httpRequestMock.Setup(m => m.Form).Returns(new NameValueCollection());
httpRequestMock.Setup(m => m.QueryString).Returns(new NameValueCollection());

Mock<HttpSessionStateBase> httpSessionStateMock = new Mock<HttpSessionStateBase>(MockBehavior.Strict);
httpSessionStateMock.Setup(m => m.SessionID).Returns(Guid.NewGuid().ToString());

Mock<HttpContextBase> HttpContextMock = new Mock<HttpContextBase>(MockBehavior.Strict);
HttpContextMock.Setup(m => m.Request).Returns(httpRequestMock.Object);
HttpContextMock.Setup(m => m.Response).Returns(httpResponseMock.Object);
HttpContextMock.Setup(m => m.Server).Returns(httpServerUtilityBaseMock.Object);
HttpContextMock.Setup(m => m.Session).Returns(httpSessionStateMock.Object);

HttpContextMock.Setup(m => m.Items).Returns(new ListDictionary());

RouteData routeData = new RouteData();
routeData.Values.Add("controller", "someController");
routeData.Values.Add("action", "index");

Mock<ControllerContext> controllerContextMock = new Mock<ControllerContext>(MockBehavior.Strict);
controllerContextMock.Setup(m => m.HttpContext).Returns(HttpContextMock.Object);
controllerContextMock.Setup(m => m.RouteData).Returns(routeData);
controllerContextMock.Setup(m => m.Controller).Returns(new AccountController());

SiteConfigurationService siteConfigurationService = SiteConfigurationService.Instance();
siteConfigurationService.LoadConfig<SiteConfigurations>(this._siteConfigurationsRepository.GetDefaultConfig());

MailingService service = new MailingService(controllerContextMock.Object, siteConfigurationService);

string result = service.RenderEmailBody<object>("/ViewToRenderToString.cshtml", new object(), controllerContextMock.Object, false);

I read HERE that the cause is that _virtualPath and HttpRuntime.AppDomainAppVirtualPathString int System.Web.VirtualPathString are NULL.

So is it possible to set them for unit testing?

Elvinelvina

I looked into this quite extensively on a previous occasion and it is difficult. What you could do instead is render your email body as usual and read it using a WebRequest or such. Then do a integration test in case you want to see how it renders. – Samons

things I did when I was trying to accomplish this without resorting to a webrequest: turn on allow .net framework stepping and/or download the mvc source code, decompile the assembly that is erroring directly. I don't think I accomplished it, but I'm VERY interested in an answer – Elegize

Answer 1

Have you tried implementing your own VirtualPathProvider?

Something like this:

public class CustomVirtualPathProvider : VirtualPathProvider
    {
        internal class CustomVirtualFile : ViewVirtualFile
        {
            public override bool IsDirectory
            {
                get
                {
                    return base.IsDirectory;
                }
            }
            public override string Name
            {
                get
                {
                    return base.Name;
                }
            }
            public override string ResourceKey
            {
                get
                {
                    return base.ResourceKey;
                }
            }
            public override System.IO.Stream Open()
            {
                return base.Open();
            }
            public CustomVirtualFile(string path)
                : base(path)
            {

            }

        }
        public override bool FileExists(string virtualPath)
        {
            return base.FileExists(virtualPath);
        }
        public override VirtualFile GetFile(string virtualPath)
        {
            return base.GetFile(virtualPath);
        }
        public override VirtualDirectory GetDirectory(string virtualDir)
        {
            return base.GetDirectory(virtualDir);
        }
        public override bool DirectoryExists(string virtualDir)
        {
            return base.DirectoryExists(virtualDir);
        }


    }

Then in Global.asax

///register our custom virtual path provider factory.
            HostingEnvironment.RegisterVirtualPathProvider(new CustomVirtualPathProvider());

With this approach, you can render views from anywhere.

Araldo

What is ViewVirtualFile? Where is it defined? And what is it needed for? – Dooryard

@JackMiller I think this intends to use VirtualFile instead. – Refurbish