Add tests of `TextAreaTagHelper`

- new Microsoft.AspNet.Mvc.TagHelpers.Test project
- bit of test infrastructure -- `TestableHtmlGenerator`
 - short-curcuits validation attribute and AntiForgery additions
 - should help when testing all MVC tag helpers

Mvc.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 14
-VisualStudioVersion = 14.0.22115.0
+VisualStudioVersion = 14.0.22209.0
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "samples", "samples", "{DAAE4C74-D06F-4874-A166-33305D2643CE}"
 EndProject
@@ -102,6 +102,8 @@ Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "TagHelperSample.Web", "samp
 EndProject
 Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "Microsoft.AspNet.Mvc.TagHelpers", "src\Microsoft.AspNet.Mvc.TagHelpers\Microsoft.AspNet.Mvc.TagHelpers.kproj", "{B2347320-308E-4D2B-AEC8-005DFA68B0C9}"
 EndProject
+Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "Microsoft.AspNet.Mvc.TagHelpers.Test", "test\Microsoft.AspNet.Mvc.TagHelpers.Test\Microsoft.AspNet.Mvc.TagHelpers.Test.kproj", "{860119ED-3DB1-424D-8D0A-30132A8A7D96}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -542,6 +544,16 @@ Global
 		{B2347320-308E-4D2B-AEC8-005DFA68B0C9}.Release|Mixed Platforms.ActiveCfg = Release|Any CPU
 		{B2347320-308E-4D2B-AEC8-005DFA68B0C9}.Release|Mixed Platforms.Build.0 = Release|Any CPU
 		{B2347320-308E-4D2B-AEC8-005DFA68B0C9}.Release|x86.ActiveCfg = Release|Any CPU
+		{860119ED-3DB1-424D-8D0A-30132A8A7D96}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{860119ED-3DB1-424D-8D0A-30132A8A7D96}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{860119ED-3DB1-424D-8D0A-30132A8A7D96}.Debug|Mixed Platforms.ActiveCfg = Debug|Any CPU
+		{860119ED-3DB1-424D-8D0A-30132A8A7D96}.Debug|Mixed Platforms.Build.0 = Debug|Any CPU
+		{860119ED-3DB1-424D-8D0A-30132A8A7D96}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{860119ED-3DB1-424D-8D0A-30132A8A7D96}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{860119ED-3DB1-424D-8D0A-30132A8A7D96}.Release|Any CPU.Build.0 = Release|Any CPU
+		{860119ED-3DB1-424D-8D0A-30132A8A7D96}.Release|Mixed Platforms.ActiveCfg = Release|Any CPU
+		{860119ED-3DB1-424D-8D0A-30132A8A7D96}.Release|Mixed Platforms.Build.0 = Release|Any CPU
+		{860119ED-3DB1-424D-8D0A-30132A8A7D96}.Release|x86.ActiveCfg = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -591,5 +603,6 @@ Global
 		{5DE8E4D9-AACD-4B5F-819F-F091383FB996} = {3BA657BF-28B1-42DA-B5B0-1C4601FCF7B1}
 		{2223120F-D675-40DA-8CD8-11DC14A0B2C7} = {DAAE4C74-D06F-4874-A166-33305D2643CE}
 		{B2347320-308E-4D2B-AEC8-005DFA68B0C9} = {32285FA4-6B46-4D6B-A840-2B13E4C8B58E}
+		{860119ED-3DB1-424D-8D0A-30132A8A7D96} = {3BA657BF-28B1-42DA-B5B0-1C4601FCF7B1}
 	EndGlobalSection
 EndGlobal

test/Microsoft.AspNet.Mvc.TagHelpers.Test/Microsoft.AspNet.Mvc.TagHelpers.Test.kproj

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">14.0</VisualStudioVersion>
+    <VSToolsPath Condition="'$(VSToolsPath)' == ''">$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)</VSToolsPath>
+  </PropertyGroup>
+
+  <Import Project="$(VSToolsPath)\AspNet\Microsoft.Web.AspNet.Props" Condition="'$(VSToolsPath)' != ''" />
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>860119ed-3db1-424d-8d0a-30132a8a7d96</ProjectGuid>
+    <RootNamespace>Microsoft.AspNet.Mvc.TagHelpers.Test</RootNamespace>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <SchemaVersion>2.0</SchemaVersion>
+  </PropertyGroup>
+  <Import Project="$(VSToolsPath)\AspNet\Microsoft.Web.AspNet.targets" Condition="'$(VSToolsPath)' != ''" />
+</Project>

test/Microsoft.AspNet.Mvc.TagHelpers.Test/TestableHtmlGenerator.cs

@@ -0,0 +1,110 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using Microsoft.AspNet.Http;
+using Microsoft.AspNet.Mvc.ModelBinding;
+using Microsoft.AspNet.Mvc.Rendering;
+using Microsoft.AspNet.Routing;
+using Microsoft.AspNet.Security.DataProtection;
+using Microsoft.Framework.OptionsModel;
+using Moq;
+
+namespace Microsoft.AspNet.Mvc.TagHelpers
+{
+    public class TestableHtmlGenerator : DefaultHtmlGenerator
+    {
+        private IDictionary<string, object> _validationAttributes;
+
+        public TestableHtmlGenerator(IModelMetadataProvider metadataProvider)
+            : this(metadataProvider, Mock.Of<IUrlHelper>())
+        {
+        }
+
+        public TestableHtmlGenerator(IModelMetadataProvider metadataProvider, IUrlHelper urlHelper)
+            : this(
+                  metadataProvider,
+                  urlHelper,
+                  validationAttributes: new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase))
+        {
+        }
+
+        public TestableHtmlGenerator(
+            IModelMetadataProvider metadataProvider,
+            IUrlHelper urlHelper,
+            IDictionary<string, object> validationAttributes)
+            : base(Mock.Of<IActionBindingContextProvider>(), GetAntiForgery(), metadataProvider, urlHelper)
+        {
+            _validationAttributes = validationAttributes;
+        }
+
+        public IDictionary<string, object> ValidationAttributes
+        {
+            get { return _validationAttributes; }
+        }
+
+        public static ViewContext GetViewContext(
+            object model,
+            IHtmlGenerator htmlGenerator,
+            IModelMetadataProvider metadataProvider)
+        {
+            var serviceProvider = new Mock<IServiceProvider>();
+            serviceProvider
+                .Setup(provider => provider.GetService(typeof(IHtmlGenerator)))
+                .Returns(htmlGenerator);
+
+            var httpContext = new Mock<HttpContext>();
+            httpContext
+                .Setup(context => context.RequestServices)
+                .Returns(serviceProvider.Object);
+
+            var actionContext = new ActionContext(httpContext.Object, new RouteData(), new ActionDescriptor());
+            var viewData = new ViewDataDictionary(metadataProvider)
+            {
+                Model = model,
+            };
+            var viewContext = new ViewContext(actionContext, Mock.Of<IView>(), viewData, new StringWriter());
+
+            return viewContext;
+        }
+
+        public override TagBuilder GenerateAntiForgery(ViewContext viewContext)
+        {
+            return new TagBuilder("input")
+            {
+                Attributes =
+                {
+                    { "name", "__RequestVerificationToken" },
+                    { "type", "hidden" },
+                    { "value", "olJlUDjrouRNWLen4tQJhauj1Z1rrvnb3QD65cmQU1Ykqi6S4" }, // 50 chars of a token.
+                },
+            };
+        }
+
+        protected override IDictionary<string, object> GetValidationAttributes(
+            ViewContext viewContext,
+            ModelMetadata metadata,
+            string name)
+        {
+            return ValidationAttributes;
+        }
+
+        private static AntiForgery GetAntiForgery()
+        {
+            // AntiForgery must be passed to TestableHtmlGenerator constructor but will never be called.
+            var optionsAccessor = new Mock<IOptionsAccessor<MvcOptions>>();
+            optionsAccessor
+                .SetupGet(o => o.Options)
+                .Returns(new MvcOptions());
+            var antiForgery = new AntiForgery(
+                Mock.Of<IClaimUidExtractor>(),
+                Mock.Of<IDataProtectionProvider>(),
+                Mock.Of<IAntiForgeryAdditionalDataProvider>(),
+                optionsAccessor.Object);
+
+            return antiForgery;
+        }
+    }
+}

test/Microsoft.AspNet.Mvc.TagHelpers.Test/TextAreaTagHelperTest.cs

@@ -0,0 +1,194 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Microsoft.AspNet.Mvc.ModelBinding;
+using Microsoft.AspNet.Mvc.Razor;
+using Microsoft.AspNet.Mvc.Rendering;
+using Microsoft.AspNet.Razor.Runtime.TagHelpers;
+using Xunit;
+
+namespace Microsoft.AspNet.Mvc.TagHelpers
+{
+    public class TextAreaTagHelperTest
+    {
+        // Model (List<Model> or Model instance), container type (Model or NestModel), model accessor,
+        // property path, expected content.
+        public static TheoryData<object, Type, Func<object>, string, string> TestDataSet
+        {
+            get
+            {
+                var modelWithNull = new Model
+                {
+                    NestedModel = new NestedModel
+                    {
+                        Text = null,
+                    },
+                    Text = null,
+                };
+                var modelWithText = new Model
+                {
+                    NestedModel = new NestedModel
+                    {
+                        Text = "inner text",
+                    },
+                    Text = "outer text",
+                };
+                var models = new List<Model>
+                {
+                    modelWithNull,
+                    modelWithText,
+                };
+
+                return new TheoryData<object, Type, Func<object>, string, string>
+                {
+                    { null, typeof(Model), () => null, "Text",
+                        Environment.NewLine },
+
+                    { modelWithNull, typeof(Model), () => modelWithNull.Text, "Text",
+                        Environment.NewLine },
+                    { modelWithText, typeof(Model), () => modelWithText.Text, "Text",
+                        Environment.NewLine + "outer text" },
+
+                    { modelWithNull, typeof(NestedModel), () => modelWithNull.NestedModel.Text, "NestedModel.Text",
+                        Environment.NewLine },
+                    { modelWithText, typeof(NestedModel), () => modelWithText.NestedModel.Text, "NestedModel.Text",
+                        Environment.NewLine + "inner text" },
+
+                        // Top-level indexing does not work end-to-end due to code generation issue #1345.
+                        // TODO: Remove above comment when #1345 is fixed.
+                    { models, typeof(Model), () => models[0].Text, "[0].Text",
+                        Environment.NewLine },
+                    { models, typeof(Model), () => models[1].Text, "[1].Text",
+                        Environment.NewLine + "outer text" },
+
+                    { models, typeof(NestedModel), () => models[0].NestedModel.Text, "[0].NestedModel.Text",
+                        Environment.NewLine },
+                    { models, typeof(NestedModel), () => models[1].NestedModel.Text, "[1].NestedModel.Text",
+                        Environment.NewLine + "inner text" },
+                };
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(TestDataSet))]
+        public async Task Process_GeneratesExpectedOutput(
+            object model,
+            Type containerType,
+            Func<object> modelAccessor,
+            string propertyPath,
+            string expectedContent)
+        {
+            // Arrange
+            var expectedAttributes = new Dictionary<string, string>
+            {
+                { "class", "form-control" },
+                { "id", propertyPath },
+                { "name", propertyPath },
+                {  "valid", "from validation attributes" },
+            };
+            var expectedTagName = "textarea";
+
+            var metadataProvider = new DataAnnotationsModelMetadataProvider();
+
+            // Property name is either nameof(Model.Text) or nameof(NestedModel.Text).
+            var metadata = metadataProvider.GetMetadataForProperty(modelAccessor, containerType, propertyName: "Text");
+            var modelExpression = new ModelExpression(propertyPath, metadata);
+            var tagHelper = new TextAreaTagHelper
+            {
+                For = modelExpression,
+            };
+
+            var tagHelperContext = new TagHelperContext(new Dictionary<string, object>());
+            var htmlAttributes = new Dictionary<string, string>
+            {
+                { "class", "form-control" },
+            };
+            var output = new TagHelperOutput("original tag name", htmlAttributes, "original content")
+            {
+                SelfClosing = true,
+            };
+
+            var htmlGenerator = new TestableHtmlGenerator(metadataProvider)
+            {
+                ValidationAttributes =
+                {
+                    {  "valid", "from validation attributes" },
+                }
+            };
+            var viewContext = TestableHtmlGenerator.GetViewContext(model, htmlGenerator, metadataProvider);
+            var activator = new DefaultTagHelperActivator();
+            activator.Activate(tagHelper, viewContext);
+
+            // Act
+            await tagHelper.ProcessAsync(tagHelperContext, output);
+
+            // Assert
+            Assert.Equal(expectedAttributes, output.Attributes);
+            Assert.Equal(expectedContent, output.Content);
+            Assert.False(output.SelfClosing);
+            Assert.Equal(expectedTagName, output.TagName);
+        }
+
+        [Fact]
+        public async Task TagHelper_LeavesOutputUnchanged_IfForNotBound()
+        {
+            // Arrange
+            var expectedAttributes = new Dictionary<string, string>
+            {
+                { "class", "form-control" },
+            };
+            var expectedContent = "original content";
+            var expectedTagName = "original tag name";
+
+            var metadataProvider = new DataAnnotationsModelMetadataProvider();
+            var metadata = metadataProvider.GetMetadataForProperty(
+                modelAccessor: () => null,
+                containerType: typeof(Model),
+                propertyName: nameof(Model.Text));
+            var modelExpression = new ModelExpression(nameof(Model.Text), metadata);
+            var tagHelper = new TextAreaTagHelper();
+
+            var tagHelperContext = new TagHelperContext(new Dictionary<string, object>());
+            var output = new TagHelperOutput(expectedTagName, expectedAttributes, expectedContent)
+            {
+                SelfClosing = true,
+            };
+
+            var htmlGenerator = new TestableHtmlGenerator(metadataProvider)
+            {
+                ValidationAttributes =
+                {
+                    {  "valid", "from validation attributes" },
+                }
+            };
+            Model model = null;
+            var viewContext = TestableHtmlGenerator.GetViewContext(model, htmlGenerator, metadataProvider);
+            var activator = new DefaultTagHelperActivator();
+            activator.Activate(tagHelper, viewContext);
+
+            // Act
+            await tagHelper.ProcessAsync(tagHelperContext, output);
+
+            // Assert
+            Assert.Equal(expectedAttributes, output.Attributes);
+            Assert.Equal(expectedContent, output.Content);
+            Assert.True(output.SelfClosing);
+            Assert.Equal(expectedTagName, output.TagName);
+        }
+
+        private class Model
+        {
+            public string Text { get; set; }
+
+            public NestedModel NestedModel { get; set; }
+        }
+
+        private class NestedModel
+        {
+            public string Text { get; set; }
+        }
+    }
+}

test/Microsoft.AspNet.Mvc.TagHelpers.Test/project.json

@@ -0,0 +1,17 @@
+{
+    "commands": {
+        "test": "Xunit.KRunner"
+    },
+    "dependencies": {
+        "Microsoft.AspNet.Mvc.TagHelpers": "6.0.0-*",
+        "Microsoft.AspNet.Testing": "1.0.0-*",
+        "Xunit.KRunner": "1.0.0-*"
+    },
+    "frameworks": {
+        "aspnet50": {
+            "dependencies": {
+                "Moq": "4.2.1312.1622"
+            }
+        }
+    }
+}