Create test for old NuGet

GeneratePathProperty does not work as seen in NuGet/Home#8476. Use workaround.

src/Build.OM.UnitTests/Microsoft.Build.Engine.OM.UnitTests.csproj

@@ -13,8 +13,18 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
 
+  <PropertyGroup>
+    <NuGetCommandLinePackageVersion>4.1.0</NuGetCommandLinePackageVersion>
+</PropertyGroup>
+
   <ItemGroup>
     <PackageReference Include="Shouldly" />
+    <PackageDownload Include="NuGet.CommandLine" Version="[$(NuGetCommandLinePackageVersion)]" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <!-- GeneratePathProperty currently isn't enabled for PackageDownload. -->
+    <Content Condition="'$(MSBuildRuntimeType)' != 'Core' and '$(Configuration)' == 'Release'" Include="$(NuGetPackageRoot)\nuget.commandline\$(NuGetCommandLinePackageVersion)\tools\NuGet.exe" CopyToOutputDirectory="PreserveNewest" Link="nuget\NuGet.exe" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFrameworkIdentifier)' != '.NETFramework'">
@@ -94,6 +104,7 @@
     <Compile Include="..\Shared\UnitTests\TestData\GlobbingTestData.cs">
       <Link>TestData\GlobbingTestData.cs</Link>
     </Compile>
+    <Compile Include="..\UnitTests.Shared\RunnerUtilities.cs" />
 
     <None Include="..\Shared\UnitTests\App.config">
       <Link>App.config</Link>

src/Build.OM.UnitTests/NugetRestoreTests.cs

@@ -0,0 +1,57 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Microsoft.Build.UnitTests;
+using Microsoft.Build.UnitTests.Shared;
+using Shouldly;
+using System.IO;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Microsoft.Build.Engine.OM.UnitTests
+{
+    public sealed class NugetRestoreTests
+    {
+        private ITestOutputHelper _output;
+        public NugetRestoreTests(ITestOutputHelper output)
+        {
+            _output = output;
+        }
+
+        // This NuGet version cannot locate other assemblies when parsing solutions at restore time. This includes localized strings required in debug mode.
+        // NuGet version 4.1.0 was somewhat arbitrarily chosen. 3.5 breaks with an unrelated error, and 4.8.2 does not fail when a new dependency is introduced. This is a safe middle point.
+#if !DEBUG
+        [SkipOnTargetFramework(TargetFrameworkMonikers.Netcoreapp)]
+        [Fact]
+        public void TestOldNuget()
+        {
+            string msbuildExePath = Path.GetDirectoryName(RunnerUtilities.PathToCurrentlyRunningMsBuildExe);
+            using TestEnvironment testEnvironment = TestEnvironment.Create();
+            TransientTestFolder folder = testEnvironment.CreateFolder(createFolder: true);
+            // The content of the solution isn't known to matter, but having a custom solution makes it easier to add requirements should they become evident.
+            TransientTestFile sln = testEnvironment.CreateFile(folder, "test.sln",
+                @"
+Microsoft Visual Studio Solution File, Format Version 12.00
+\# Visual Studio 15
+VisualStudioVersion = 15.0.26124.0
+MinimumVisualStudioVersion = 15.0.26124.0
+Global
+GlobalSection(SolutionConfigurationPlatforms) = preSolution
+	Debug|Any CPU = Debug|Any CPU
+	Debug|x64 = Debug|x64
+	Debug|x86 = Debug|x86
+	Release|Any CPU = Release|Any CPU
+	Release|x64 = Release|x64
+	Release|x86 = Release|x86
+EndGlobalSection
+GlobalSection(SolutionProperties) = preSolution
+	HideSolutionNode = FALSE
+EndGlobalSection
+EndGlobal
+");
+            RunnerUtilities.RunProcessAndGetOutput(Path.Combine(msbuildExePath, "nuget", "NuGet.exe"), "restore " + sln.Path + " -MSBuildPath \"" + msbuildExePath + "\"", out bool success, outputHelper: _output);
+            success.ShouldBeTrue();
+        }
+#endif
+    }
+}