Add tests for map path without wwwroot, and typos

src/Microsoft.AspNet.Hosting.Abstractions/HostingEnvironmentExtensions.cs

@@ -93,7 +93,7 @@ namespace Microsoft.AspNet.Hosting
             }
             if (string.IsNullOrEmpty(hostingEnvironment.WebRootPath))
             {
-                throw new InvalidOperationException("Can not map path because webroot path is not set");
+                throw new InvalidOperationException("Cannot map path because webroot path is not set");
             }
             if (virtualPath == null)
             {

test/Microsoft.AspNet.Hosting.Tests/HostingEnvironmentExtensionsTests.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. 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.IO;
 using Microsoft.AspNet.FileProviders;
 using Microsoft.AspNet.Hosting;
@@ -67,5 +68,15 @@ namespace Microsoft.AspNet.Hosting.Tests
             Assert.Equal("NewName", env.EnvironmentName);
         }
 
+        [Fact]
+        public void MapPathThrowsWithNoWwwroot()
+        {
+            var env = new HostingEnvironment();
+
+            env.Initialize(".", new WebHostOptions(), null);
+
+            Assert.Throws<InvalidOperationException>(() => env.MapPath("file.txt"));
+        }
+
     }
 }

test/Microsoft.AspNet.Hosting.Tests/testroot/wwwroot/README

@@ -1 +1 @@
-This file is here to keep directories needed by tests. Do no remove it.
+This file is here to keep directories needed by tests. Do not remove it.