Enable us to unit test `@Html...For()` methods

- add more `DefaultTemplatesUtilities.GetHtmlHelper()` overloads, all
  returning a strongly-typed helper
- also correct that method to ensure template helpers each get a unique
  `IHtmlHelper` instance

test/Microsoft.AspNet.Mvc.Core.Test/Rendering/DefaultDisplayTemplatesTests.cs

@@ -39,7 +39,7 @@ namespace Microsoft.AspNet.Mvc.Core.Test
         public void ObjectTemplateDisplaysNullDisplayTextWhenObjectIsNull()
         {
             // Arrange
-            var html = DefaultTemplatesUtilities.GetHtmlHelper(null);
+            var html = DefaultTemplatesUtilities.GetHtmlHelper();
             var metadata =
                 new EmptyModelMetadataProvider()
                     .GetMetadataForType(null, typeof(DefaultTemplatesUtilities.ObjectTemplateModel));

test/Microsoft.AspNet.Mvc.Core.Test/Rendering/DefaultEditorTemplatesTests.cs

@@ -39,7 +39,7 @@ namespace Microsoft.AspNet.Mvc.Core.Test
         public void ObjectTemplateDisplaysNullDisplayTextWithNullModelAndTemplateDepthGreaterThanOne()
         {
             // Arrange
-            var html = DefaultTemplatesUtilities.GetHtmlHelper(null);
+            var html = DefaultTemplatesUtilities.GetHtmlHelper();
             var metadata =
                 new EmptyModelMetadataProvider()
                     .GetMetadataForType(null, typeof(DefaultTemplatesUtilities.ObjectTemplateModel));
@@ -83,11 +83,15 @@ namespace Microsoft.AspNet.Mvc.Core.Test
         {
             // Arrange
             var expected =
-@"<div class=""editor-label""><label for=""Property1"">Property1</label></div>
+@"<div class=""editor-label""><label for=""Property1"">Property1</label></div>" +
-<div class=""editor-field""><input class=""text-box single-line"" id=""Property1"" name=""Property1"" type=""text"" value="""" /> </div>
+Environment.NewLine +
-<div class=""editor-label""><label for=""Property1.Property3"">Property3</label></div>
+@"<div class=""editor-field""><input class=""text-box single-line"" id=""Property1"" name=""Property1"" type=""text"" value="""" /> </div>" +
-<div class=""editor-field""> </div>
+Environment.NewLine +
-";
+@"<div class=""editor-label""><label for=""Property3"">Property3</label></div>" +
+Environment.NewLine +
+@"<div class=""editor-field""><input class=""text-box single-line"" id=""Property3"" name=""Property3"" type=""text"" value="""" /> </div>" +
+Environment.NewLine;
+
             var model = new DefaultTemplatesUtilities.ObjectWithScaffoldColumn();
             var viewEngine = new Mock<IViewEngine>();
             viewEngine.Setup(v => v.FindPartialView(It.IsAny<IDictionary<string, object>>(), It.IsAny<string>()))

test/Microsoft.AspNet.Mvc.Core.Test/Rendering/DefaultTemplatesUtilities.cs

@@ -16,7 +16,7 @@ using Microsoft.AspNet.Security.DataProtection;
 using Microsoft.Framework.OptionsModel;
 using Moq;
 
-namespace Microsoft.AspNet.Mvc.Core.Test
+namespace Microsoft.AspNet.Mvc.Core
 {
     public class DefaultTemplatesUtilities
     {
@@ -43,14 +43,38 @@ namespace Microsoft.AspNet.Mvc.Core.Test
             public string Property3 { get; set; }
         }
 
-        public static HtmlHelper GetHtmlHelper(object model,
+        public static HtmlHelper<ObjectTemplateModel> GetHtmlHelper()
-                                               IViewEngine viewEngine = null)
         {
-            var provider = new DataAnnotationsModelMetadataProvider();
+            return GetHtmlHelper<ObjectTemplateModel>(null);
-            var viewData = new ViewDataDictionary(provider);
+        }
+
+        public static HtmlHelper<TModel> GetHtmlHelper<TModel>(TModel model)
+        {
+            return GetHtmlHelper(model, CreateViewEngine());
+        }
+
+        public static HtmlHelper<ObjectTemplateModel> GetHtmlHelper(IModelMetadataProvider provider)
+        {
+            return GetHtmlHelper<ObjectTemplateModel>(null, provider);
+        }
+
+        public static HtmlHelper<TModel> GetHtmlHelper<TModel>(TModel model, IModelMetadataProvider provider)
+        {
+            return GetHtmlHelper(model, CreateViewEngine(), provider);
+        }
+
+        public static HtmlHelper<TModel> GetHtmlHelper<TModel>(TModel model, IViewEngine viewEngine)
+        {
+            return GetHtmlHelper(model, viewEngine, new DataAnnotationsModelMetadataProvider());
+        }
+
+        public static HtmlHelper<TModel> GetHtmlHelper<TModel>(
+            TModel model,
+            IViewEngine viewEngine,
+            IModelMetadataProvider provider)
+        {
+            var viewData = new ViewDataDictionary<TModel>(provider);
             viewData.Model = model;
-            viewData.ModelMetadata =
-                provider.GetMetadataForType(() => model, typeof(ObjectTemplateModel));
 
             var httpContext = new Mock<HttpContext>();
             httpContext
@@ -60,8 +84,6 @@ namespace Microsoft.AspNet.Mvc.Core.Test
                 .Setup(o => o.Items)
                 .Returns(new Dictionary<object, object>());
 
-            viewEngine = viewEngine ?? CreateViewEngine();
-
             var actionContext = new ActionContext(httpContext.Object,
                                       new RouteData(),
                                       new ActionDescriptor());
@@ -95,18 +117,23 @@ namespace Microsoft.AspNet.Mvc.Core.Test
 
             var viewContext = new ViewContext(actionContext, Mock.Of<IView>(), viewData, new StringWriter());
 
-            var htmlHelper = new HtmlHelper(
+            // TemplateRenderer will Contextualize this transient service.
-                                    viewEngine,
-                                    provider,
-                                    urlHelper,
-                                    GetAntiForgeryInstance(),
-                                    actionBindingContextProvider.Object);
-            htmlHelper.Contextualize(viewContext);
-
             serviceProvider
                 .Setup(s => s.GetService(typeof(IHtmlHelper)))
-                .Returns(htmlHelper);
+                .Returns(() => new HtmlHelper(
+                    viewEngine,
+                    provider,
+                    urlHelper,
+                    GetAntiForgeryInstance(),
+                    actionBindingContextProvider.Object));
 
+            var htmlHelper = new HtmlHelper<TModel>(
+                viewEngine,
+                provider,
+                urlHelper,
+                GetAntiForgeryInstance(),
+                actionBindingContextProvider.Object);
+            htmlHelper.Contextualize(viewContext);
 
             return htmlHelper;
         }