Move few GivenWeWantToRequireWindowsForDesktopApps tests (#8205)

Fix https://github.com/dotnet/installer/issues/8203

test/EndToEnd/GivenWeWantToRequireWindowsForDesktopApps.cs

@@ -0,0 +1,62 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.IO;
+using EndToEnd;
+using FluentAssertions;
+using Microsoft.DotNet.Tools.Test.Utilities;
+using Xunit;
+
+namespace Microsoft.DotNet.Tests.EndToEnd
+{
+    public class GivenWeWantToRequireWindowsForDesktopApps
+    {
+        [Fact]
+        public void It_does_not_download_desktop_targeting_packs_on_unix()
+        {
+            var testProjectCreator = new TestProjectCreator()
+            {
+                MinorVersion = "5.0"
+            };
+
+            testProjectCreator.AdditionalProperties["RestorePackagesPath"] = @"$(MSBuildProjectDirectory)\packages";
+            testProjectCreator.AdditionalProperties["OutputType"] = "exe";
+
+            var testInstance = testProjectCreator.Create();
+
+            new BuildCommand()
+                    .WithWorkingDirectory(testInstance.Root.FullName)
+                    .Execute()
+                    .Should().Pass();
+
+            string packagesPath = Path.Combine(testInstance.Root.FullName, "packages");
+            Directory.Exists(packagesPath).Should().BeFalse(packagesPath + " should not exist");
+        }
+
+        [PlatformSpecificFact(TestPlatforms.Linux | TestPlatforms.OSX | TestPlatforms.FreeBSD)]
+        public void It_does_not_download_desktop_runtime_packs_on_unix()
+        {
+            const string Rid = "win-x64";
+
+            var testProjectCreator = new TestProjectCreator()
+            {
+                MinorVersion = "3.1"
+            };
+
+            testProjectCreator.AdditionalProperties["RestorePackagesPath"] = @"$(MSBuildProjectDirectory)\packages";
+            testProjectCreator.AdditionalProperties["OutputType"] = "exe";
+            testProjectCreator.AdditionalProperties["RuntimeIdentifier"] = Rid;
+
+            var testInstance = testProjectCreator.Create();
+
+            new PublishCommand()
+                    .WithWorkingDirectory(testInstance.Root.FullName)
+                    .Execute()
+                    .Should().Pass();
+
+            string packagesPath = Path.Combine(testInstance.Root.FullName, "packages", $"runtime.{Rid}.microsoft.windowsdesktop.app"); 
+            Directory.Exists(packagesPath).Should().BeFalse(packagesPath + " should not exist");
+        }
+    }
+}

test/EndToEnd/TestProjectCreator.cs

@@ -25,6 +25,8 @@ namespace EndToEnd
 
         public string RuntimeIdentifier { get; set; }
 
+        public Dictionary<string, string> AdditionalProperties { get; } = new Dictionary<string, string>();
+
         public TestProjectCreator([CallerMemberName] string testName = null, string identifier = "")
         {
             TestName = testName;
@@ -54,7 +56,11 @@ namespace EndToEnd
                 project.Root.Element(ns + "PropertyGroup")
                     .Add(new XElement(ns + "RuntimeIdentifier", RuntimeIdentifier));
             }
-            
+
+            foreach (var additionalProperty in AdditionalProperties)
+            {
+                project.Root.Element(ns + "PropertyGroup").Add(new XElement(ns + additionalProperty.Key, additionalProperty.Value));
+            }
 
             if (PackageName != NETCorePackageName)
             {

test/Microsoft.DotNet.Tools.Tests.Utilities/PlatformSpecificFact.cs

@@ -0,0 +1,44 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Runtime.InteropServices;
+using Xunit;
+
+namespace Microsoft.DotNet.Tools.Test.Utilities
+{
+    public class PlatformSpecificFact : FactAttribute
+    {
+        public PlatformSpecificFact(TestPlatforms platforms)
+        {
+            if (ShouldSkip(platforms))
+            {
+                this.Skip = "This test is not supported on this platform.";
+            }
+        }
+
+        internal static bool ShouldSkip(TestPlatforms platforms) =>
+            (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !platforms.HasFlag(TestPlatforms.Windows))
+                || (RuntimeInformation.IsOSPlatform(OSPlatform.Linux) && !platforms.HasFlag(TestPlatforms.Linux))
+                || (RuntimeInformation.IsOSPlatform(OSPlatform.OSX) && !platforms.HasFlag(TestPlatforms.OSX))
+                || (RuntimeInformation.IsOSPlatform(OSPlatform.Create("FREEBSD")) && !platforms.HasFlag(TestPlatforms.FreeBSD));
+    }
+
+    [Flags]
+    public enum TestPlatforms
+    {
+        Any = -1,
+        Windows = 1,
+        Linux = 2,
+        OSX = 4,
+        FreeBSD = 8,
+        NetBSD = 16,
+        illumos = 32,
+        Solaris = 64,
+        iOS = 128,
+        tvOS = 256,
+        Android = 512,
+        Browser = 1024,
+        AnyUnix = 2048
+    }
+}

test/Microsoft.DotNet.Tools.Tests.Utilities/PlatformSpecificTheory.cs

@@ -0,0 +1,18 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Xunit;
+
+namespace Microsoft.DotNet.Tools.Test.Utilities
+{
+    public class PlatformSpecificTheory : TheoryAttribute
+    {
+        public PlatformSpecificTheory(TestPlatforms platforms)
+        {
+            if (PlatformSpecificFact.ShouldSkip(platforms))
+            {
+                this.Skip = "This test is not supported on this platform.";
+            }
+        }
+    }
+}