Add TaskExtensions.Unwrap tests

This commit provides a System.Threading.Tasks.Tests project that doesn't include all of the tests that @mellinoe is porting.  However, it does include a new set of tests written from scratch for TaskExtensions.Unwrap, which is the portion of System.Threading.Tasks whose source lives in corefx rather than in coreclr.  They are meant to be the primary unit testing for Unwrap, as the existing tests only superficially exercise the functionality.

Author: stephentoub

src/System.Threading.Tasks/System.Threading.Tasks.sln

@@ -1,10 +1,12 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio 2013
-VisualStudioVersion = 12.0.30723.0
+# Visual Studio 14
+VisualStudioVersion = 14.0.22823.1
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "System.Threading.Tasks.CoreCLR", "src\System.Threading.Tasks.CoreCLR.csproj", "{3BCAEAA6-3A29-49EC-B334-6E7BE8BE9ABA}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "System.Threading.Tasks.Tests", "tests\System.Threading.Tasks.Tests.csproj", "{B6C09633-D161-499A-8FE1-46B2D53A16E7}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -15,6 +17,10 @@ Global
 		{3BCAEAA6-3A29-49EC-B334-6E7BE8BE9ABA}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{3BCAEAA6-3A29-49EC-B334-6E7BE8BE9ABA}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{3BCAEAA6-3A29-49EC-B334-6E7BE8BE9ABA}.Release|Any CPU.Build.0 = Release|Any CPU
+		{B6C09633-D161-499A-8FE1-46B2D53A16E7}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{B6C09633-D161-499A-8FE1-46B2D53A16E7}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{B6C09633-D161-499A-8FE1-46B2D53A16E7}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{B6C09633-D161-499A-8FE1-46B2D53A16E7}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

src/System.Threading.Tasks/tests/System.Threading.Tasks.Tests.csproj

@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="12.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.props))\dir.props" />
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <OutputType>Library</OutputType>
+    <AssemblyName>System.Threading.Tasks.Tests</AssemblyName>
+    <ProjectGuid>{B6C09633-D161-499A-8FE1-46B2D53A16E7}</ProjectGuid>
+  </PropertyGroup>
+  <!-- Default configurations to help VS understand the configurations -->
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' " />
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' " />
+  <ItemGroup>
+    <Compile Include="UnwrapTests.cs" />
+  </ItemGroup>
+  <ItemGroup>
+    <None Include="project.json" />
+  </ItemGroup>
+  <ItemGroup>
+    <!-- Compile tests against the System.Runtime contract, but copy our local-built implementation for testing -->
+    <ProjectReference Include="..\src\System.Threading.Tasks.CoreCLR.csproj">
+      <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
+      <OutputItemType>Content</OutputItemType>
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+      <Targets>Build;DebugSymbolsProjectOutputGroup</Targets>
+    </ProjectReference>
+  </ItemGroup>
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
+</Project>