Test TagHelperScopeManager functionality.

#155

test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/TagHelperScopeManagerTest.cs

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+// 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 Microsoft.AspNet.Razor.Runtime.TagHelpers;
+using Xunit;
+
+namespace Microsoft.AspNet.Razor.Runtime.Test.TagHelpers
+{
+    public class TagHelperScopeManagerTest
+    {
+        [Fact]
+        public void TagHelperScopeManager_BeginCreatesContextWithAppropriateTagName()
+        {
+            // Arrange
+            var scopeManager = new TagHelperScopeManager();
+
+            // Act
+            var executionContext = scopeManager.Begin("p");
+
+            // Assert
+            Assert.Equal("p", executionContext.TagName);
+        }
+
+        [Fact]
+        public void TagHelperScopeManager_BeginCanNest()
+        {
+            // Arrange
+            var scopeManager = new TagHelperScopeManager();
+
+            // Act
+            var executionContext = scopeManager.Begin("p");
+            executionContext = scopeManager.Begin("div");
+
+            // Assert
+            Assert.Equal("div", executionContext.TagName);
+        }
+
+        [Fact]
+        public void TagHelperScopeManager_EndReturnsParentExecutionContext()
+        {
+            // Arrange
+            var scopeManager = new TagHelperScopeManager();
+
+            // Act
+            var executionContext = scopeManager.Begin("p");
+            executionContext = scopeManager.Begin("div");
+            executionContext = scopeManager.End();
+
+            // Assert
+            Assert.Equal("p", executionContext.TagName);
+        }
+
+        [Fact]
+        public void TagHelperScopeManager_EndReturnsNullIfNoNestedContext()
+        {
+            // Arrange
+            var scopeManager = new TagHelperScopeManager();
+
+            // Act
+            var executionContext = scopeManager.Begin("p");
+            executionContext = scopeManager.Begin("div");
+            executionContext = scopeManager.End();
+            executionContext = scopeManager.End();
+
+            // Assert
+            Assert.Null(executionContext);
+        }
+
+        [Fact]
+        public void TagHelperScopeManager_EndThrowsIfNoScope()
+        {
+            // Arrange
+            var scopeManager = new TagHelperScopeManager();
+            var expectedError =
+                "You cannot call 'End' without first calling 'Begin' on the " + nameof(TagHelperScopeManager) + ".";
+
+            // Act & Assert
+            var ex = Assert.Throws<InvalidOperationException>(() =>
+            {
+                scopeManager.End();
+            });
+
+            Assert.Equal(expectedError, ex.Message);
+
+        }
+    }
+}