Fixing PathString.Add(PathString) to handle trailing slashes correctly

Fixes #31

HttpAbstractions.sln

@@ -37,6 +37,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Microsoft.AspNet.FeatureMod
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Microsoft.AspNet.PipelineCore.Tests.net45", "test\Microsoft.AspNet.PipelineCore.Tests\Microsoft.AspNet.PipelineCore.Tests.net45.csproj", "{00A03235-B248-4079-A7EE-4F77AB3A84E4}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Microsoft.AspNet.Abstractions.Tests.net45", "test\Microsoft.AspNet.Abstractions.Tests\Microsoft.AspNet.Abstractions.Tests.net45.csproj", "{EE4DFB8C-FDD8-4A6E-97B7-AE6E663EE5D0}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -91,6 +93,10 @@ Global
 		{00A03235-B248-4079-A7EE-4F77AB3A84E4}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{00A03235-B248-4079-A7EE-4F77AB3A84E4}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{00A03235-B248-4079-A7EE-4F77AB3A84E4}.Release|Any CPU.Build.0 = Release|Any CPU
+		{EE4DFB8C-FDD8-4A6E-97B7-AE6E663EE5D0}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{EE4DFB8C-FDD8-4A6E-97B7-AE6E663EE5D0}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{EE4DFB8C-FDD8-4A6E-97B7-AE6E663EE5D0}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{EE4DFB8C-FDD8-4A6E-97B7-AE6E663EE5D0}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -111,5 +117,6 @@ Global
 		{04077455-D4A2-43AF-ABA2-E68968856E17} = {F31FF137-390C-49BF-A3BD-7C6ED3597C21}
 		{4C82EE1A-9B93-4374-91E0-75476AABF5CD} = {04077455-D4A2-43AF-ABA2-E68968856E17}
 		{00A03235-B248-4079-A7EE-4F77AB3A84E4} = {04077455-D4A2-43AF-ABA2-E68968856E17}
+		{EE4DFB8C-FDD8-4A6E-97B7-AE6E663EE5D0} = {04077455-D4A2-43AF-ABA2-E68968856E17}
 	EndGlobalSection
 EndGlobal

src/Microsoft.AspNet.Abstractions/PathString.cs

@@ -127,6 +127,15 @@ namespace Microsoft.AspNet.Abstractions
         /// <returns>The combined PathString value</returns>
         public PathString Add(PathString other)
         {
+            if (HasValue && 
+                other.HasValue && 
+                Value[Value.Length - 1] == '/')
+            {
+                // If the path string has a trailing slash and the other string has a leading slash, we need
+                // to trim one of them.
+                return new PathString(Value + other.Value.Substring(1));
+            }
+
             return new PathString(Value + other.Value);
         }
 

test/Microsoft.AspNet.Abstractions.Tests/PathStringTests.cs

@@ -0,0 +1,51 @@
+using Microsoft.AspNet.Testing;
+using Xunit;
+
+namespace Microsoft.AspNet.Abstractions
+{
+    public class PathStringTests
+    {
+        [Fact]
+        public void CtorThrows_IfPathDoesNotHaveLeadingSlash()
+        {
+            // Act and Assert
+            ExceptionAssert.ThrowsArgument(() => new PathString("hello"), "value", "");
+        }
+
+        [Theory]
+        [InlineData(null, null)]
+        [InlineData("", null)]
+        public void AddPathString_HandlesNullAndEmptyStrings(string appString, string concatString)
+        {
+            // Arrange
+            var appPath = new PathString(appString);
+            var concatPath = new PathString(concatString);
+
+            // Act
+            var result = appPath.Add(concatPath);
+
+            // Assert
+            Assert.False(result.HasValue);
+        }
+
+        [Theory]
+        [InlineData("", "/", "/")]
+        [InlineData("/", null, "/")]
+        [InlineData("/", "", "/")]
+        [InlineData("/", "/test", "/test")]
+        [InlineData("/myapp/", "/test/bar", "/myapp/test/bar")]
+        [InlineData("/myapp/", "/test/bar/", "/myapp/test/bar/")]
+        public void AddPathString_HandlesLeadingAndTrailingSlashes(string appString, string concatString, string expected)
+        {
+            // Arrange
+            var appPath = new PathString(appString);
+            var concatPath = new PathString(concatString);
+
+            // Act
+            var result = appPath.Add(concatPath);
+
+            // Assert
+            Assert.Equal(expected, result.Value);
+        }
+    }
+}

test/Microsoft.AspNet.Abstractions.Tests/project.json

@@ -0,0 +1,23 @@
+{
+  "version": "0.1-alpha-*",
+  "dependencies": {
+    "Microsoft.AspNet.Abstractions": "",
+    "Microsoft.AspNet.Testing": "0.1-alpha-*",
+    "Xunit.KRunner": "0.1-alpha-*",
+    "xunit.abstractions": "2.0.0-aspnet-*",
+    "xunit.assert": "2.0.0-aspnet-*",
+    "xunit.core": "2.0.0-aspnet-*",
+    "xunit.execution": "2.0.0-aspnet-*"
+  },
+  "commands": {
+    "test": "Xunit.KRunner"
+  },
+  "configurations": {
+    "net45": { 
+      "dependencies": {
+        "System.Runtime":  "",
+        "Shouldly": "1.1.1.1"
+      }
+    }
+  }
+}