Make our unit tests support library (Avalonia.UnitTests) target netstandard2.0 so we don't have to worry about targetting .NET Framework on linux.

Avalonia.sln

@@ -1813,7 +1813,6 @@ Global
 		{4A1ABB09-9047-4BD5-A4AD-A055E52C5EE0}.Debug|iPhoneSimulator.ActiveCfg = Debug|Any CPU
 		{4A1ABB09-9047-4BD5-A4AD-A055E52C5EE0}.Debug|iPhoneSimulator.Build.0 = Debug|Any CPU
 		{4A1ABB09-9047-4BD5-A4AD-A055E52C5EE0}.Debug|NetCoreOnly.ActiveCfg = Debug|Any CPU
-		{4A1ABB09-9047-4BD5-A4AD-A055E52C5EE0}.Debug|NetCoreOnly.Build.0 = Debug|Any CPU
 		{4A1ABB09-9047-4BD5-A4AD-A055E52C5EE0}.Debug|x86.ActiveCfg = Debug|Any CPU
 		{4A1ABB09-9047-4BD5-A4AD-A055E52C5EE0}.Debug|x86.Build.0 = Debug|Any CPU
 		{4A1ABB09-9047-4BD5-A4AD-A055E52C5EE0}.Release|Any CPU.ActiveCfg = Release|Any CPU

src/Avalonia.Controls/AppBuilderBase.cs

@@ -209,16 +209,7 @@ namespace Avalonia.Controls
 
         public TAppBuilder UseAvaloniaModules() => AfterSetup(builder => SetupAvaloniaModules());
 
-        private bool CheckSetup { get; set; } = true;
-
-        /// <summary>
-        /// Set this AppBuilder to ignore the setup check. Used for testing purposes.
-        /// </summary>
-        internal TAppBuilder IgnoreSetupCheck()
-        {
-            CheckSetup = false;
-            return Self;
-        }
+        protected virtual bool CheckSetup => true;
 
         private void SetupAvaloniaModules()
         {

tests/Avalonia.Controls.UnitTests/AppBuilderTests.cs

@@ -6,6 +6,7 @@ using System.Threading.Tasks;
 using Xunit;
 using Avalonia.Controls.UnitTests;
 using Avalonia.Platform;
+using Avalonia.UnitTests;
 
 [assembly: ExportAvaloniaModule("DefaultModule", typeof(AppBuilderTests.DefaultModule))]
 [assembly: ExportAvaloniaModule("RenderingModule", typeof(AppBuilderTests.Direct2DModule), ForRenderingSubsystem = "Direct2D1")]
@@ -65,7 +66,6 @@ namespace Avalonia.Controls.UnitTests
             {
                 ResetModuleLoadStates();
                 AppBuilder.Configure<App>()
-                    .IgnoreSetupCheck()
                     .UseWindowingSubsystem(() => { })
                     .UseRenderingSubsystem(() => { })
                     .UseAvaloniaModules()
@@ -82,7 +82,6 @@ namespace Avalonia.Controls.UnitTests
             {
                 ResetModuleLoadStates();
                 var builder = AppBuilder.Configure<App>()
-                    .IgnoreSetupCheck()
                     .UseWindowingSubsystem(() => { })
                     .UseRenderingSubsystem(() => { }, "Direct2D1");
                 builder.UseAvaloniaModules().SetupWithoutStarting();
@@ -92,7 +91,6 @@ namespace Avalonia.Controls.UnitTests
 
                 ResetModuleLoadStates();
                 builder = AppBuilder.Configure<App>()
-                    .IgnoreSetupCheck()
                     .UseWindowingSubsystem(() => { })
                     .UseRenderingSubsystem(() => { }, "Skia");
                 builder.UseAvaloniaModules().SetupWithoutStarting();
@@ -109,7 +107,6 @@ namespace Avalonia.Controls.UnitTests
             {
                 ResetModuleLoadStates();
                 var builder = AppBuilder.Configure<App>()
-                    .IgnoreSetupCheck()
                     .UseWindowingSubsystem(() => { })
                     .UseRenderingSubsystem(() => { }, "TBD");
                 builder.UseAvaloniaModules().SetupWithoutStarting();

tests/Avalonia.DesignerSupport.TestApp/Avalonia.DesignerSupport.TestApp.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp2.0</TargetFramework>    
+    <TargetFramework>netcoreapp2.0</TargetFramework> 
   </PropertyGroup>
   <ItemGroup>
     <Compile Update="**\*.xaml.cs">

tests/Avalonia.DesignerSupport.Tests/DesignerSupportTests.cs

@@ -19,6 +19,12 @@ namespace Avalonia.DesignerSupport.Tests
     public class DesignerSupportTests
     {
         private const string DesignerAppPath = "../../../../../src/tools/Avalonia.Designer.HostApp/bin/$BUILD/netcoreapp2.0/Avalonia.Designer.HostApp.dll";
+        private readonly Xunit.Abstractions.ITestOutputHelper outputHelper;
+
+        public DesignerSupportTests(Xunit.Abstractions.ITestOutputHelper outputHelper)
+        {
+            this.outputHelper = outputHelper;
+        }
 
         [SkippableTheory,
          InlineData(
@@ -73,6 +79,8 @@ namespace Avalonia.DesignerSupport.Tests
                     }
                     else if (msg is UpdateXamlResultMessage result)
                     {
+                        if (result.Error != null)
+                            outputHelper.WriteLine(result.Error);
                         handle = result.Handle != null ? long.Parse(result.Handle) : 0;
                         resultMessageReceivedToken.Cancel();
                         conn.Dispose();

tests/Avalonia.Layout.UnitTests/FullLayoutTests.cs

@@ -21,6 +21,7 @@ using Xunit;
 using Avalonia.Media;
 using System;
 using System.Collections.Generic;
+using Avalonia.UnitTests;
 
 namespace Avalonia.Layout.UnitTests
 {

tests/Avalonia.UnitTests/Avalonia.UnitTests.csproj

@@ -1,22 +1,10 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0;net461</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0</TargetFrameworks>
     <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
     <OutputType>Library</OutputType>
   </PropertyGroup>
-  <ItemGroup Condition="'$(TargetFramework)' == 'net461'">
-    <Reference Include="System" />
-    <Reference Include="System.Core" />
-    <Reference Include="System.Xml.Linq" />
-    <Reference Include="System.Data.DataSetExtensions" />
-    <Reference Include="Microsoft.CSharp" />
-    <Reference Include="System.Data" />
-    <Reference Include="System.Net.Http" />
-    <Reference Include="System.Xml" />
-  </ItemGroup>
   <ItemGroup>
-    <ProjectReference Condition="'$(TargetFramework)' == 'net461'" Include="..\..\src\Avalonia.DotNetFrameworkRuntime\Avalonia.DotNetFrameworkRuntime.csproj" />
-    <ProjectReference Condition="'$(TargetFramework)' == 'netcoreapp2.0'" Include="..\..\src\Avalonia.DotNetCoreRuntime\Avalonia.DotNetCoreRuntime.csproj" />
     <ProjectReference Include="..\..\src\Markup\Avalonia.Markup.Xaml\Avalonia.Markup.Xaml.csproj" />
     <ProjectReference Include="..\..\src\Markup\Avalonia.Markup\Avalonia.Markup.csproj" />
     <ProjectReference Include="..\..\src\Avalonia.Animation\Avalonia.Animation.csproj" />
@@ -29,11 +17,7 @@
     <ProjectReference Include="..\..\src\Avalonia.Styling\Avalonia.Styling.csproj" />
     <ProjectReference Include="..\..\src\Avalonia.Themes.Default\Avalonia.Themes.Default.csproj" />
   </ItemGroup>
-  <ItemGroup>
-    <None Include="app.config" />
-  </ItemGroup>
   <Import Project="..\..\build\Moq.props" />
   <Import Project="..\..\build\Rx.props" />
-  <Import Project="..\..\build\XUnit.props" />
-  <Import Project="..\..\build\NetFX.props" />
+  <Import Project="..\..\src\Shared\PlatformSupport\PlatformSupport.projitems" Label="Shared" />
 </Project>

tests/Avalonia.UnitTests/RuntimeInfo.cs

@@ -0,0 +1,16 @@
+using Avalonia.Platform;
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using System.Text;
+
+namespace Avalonia.Shared.PlatformSupport
+{
+    internal partial class StandardRuntimePlatform : IRuntimePlatform
+    {
+        public RuntimePlatformInfo GetRuntimeInfo()
+        {
+            return new RuntimePlatformInfo();
+        }
+    }
+}

tests/Avalonia.UnitTests/TestServices.cs

@@ -14,6 +14,8 @@ using Avalonia.Themes.Default;
 using Avalonia.Rendering;
 using System.Reactive.Concurrency;
 using System.Collections.Generic;
+using Avalonia.Controls;
+using System.Reflection;
 
 namespace Avalonia.UnitTests
 {
@@ -178,4 +180,16 @@ namespace Avalonia.UnitTests
                     y => y.Open() == Mock.Of<IStreamGeometryContextImpl>()));
         }
     }
+
+    public class AppBuilder : AppBuilderBase<AppBuilder>
+    {
+        public AppBuilder()
+            : base(new StandardRuntimePlatform(),
+                  builder => StandardRuntimePlatformServices.Register(builder.Instance?.GetType()
+                      ?.GetTypeInfo().Assembly))
+        {
+        }
+
+        protected override bool CheckSetup => false;
+    }
 }

tests/Avalonia.UnitTests/app.config

@@ -1,11 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<configuration>
-  <runtime>
-    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
-      <dependentAssembly>
-        <assemblyIdentity name="Moq" publicKeyToken="69f491c39445e920" culture="neutral" />
-        <bindingRedirect oldVersion="0.0.0.0-4.2.1510.2205" newVersion="4.2.1510.2205" />
-      </dependentAssembly>
-    </assemblyBinding>
-  </runtime>
-</configuration>