Disable parallel mode for test collections and reenable flaky tests.

Directory.Build.props

@@ -28,6 +28,10 @@
     <EnableTrimAnalyzer Condition="$(IsTestProject) or $(IsAnalyzerProject) or $(MSBuildProjectDirectory.Contains('\tests\'))">false</EnableTrimAnalyzer>
   </PropertyGroup>
 
+  <PropertyGroup Condition="'$(IsTestProject)' == 'true'">
+    <XUnitCoreSettingsFile>$(RepositoryEngineeringDir)xunit.runner.json</XUnitCoreSettingsFile>
+  </PropertyGroup>
+
   <!--
     Set assembly version to align with major and minor version, as for the patches and revisions should be manually
     updated per assembly if it is serviced.

eng/xunit.runner.json

@@ -0,0 +1,5 @@
+{
+  "maxParallelThreads": 1,
+  "parallelizeTestCollections": false,
+  "re-run-failed-tests": 1
+}

src/Microsoft.VisualBasic.Forms/tests/UnitTests/Microsoft.VisualBasic.Forms.Tests.vbproj

@@ -22,5 +22,4 @@
     <!-- workaround for https://github.com/dotnet/sdk/issues/3254 -->
     <Reference Include="$(BaseOutputPath)..\System.Drawing.Facade\$(Configuration)\$(TargetFramework)\System.Drawing.dll" />
   </ItemGroup>
-
 </Project>

src/Microsoft.VisualBasic/tests/IntegrationTests/Microsoft.VisualBasic.IntegrationTests/Microsoft.VisualBasic.IntegrationTests.csproj

@@ -5,5 +5,4 @@
     <ProjectReference Include="..\..\..\..\System.Windows.Forms\tests\IntegrationTests\System.Windows.Forms.IntegrationTests.Common\System.Windows.Forms.IntegrationTests.Common.csproj" />
     <ProjectReference Include="..\VisualBasicRuntimeTest\VisualBasicRuntimeTest.csproj" />
   </ItemGroup>
-
 </Project>

src/Microsoft.VisualBasic/tests/IntegrationTests/VisualBasicRuntimeTest/VisualBasicRuntimeTest.csproj

@@ -7,5 +7,4 @@
   <ItemGroup>
     <ProjectReference Include="..\..\..\src\Microsoft.VisualBasic.Facade.csproj" />
   </ItemGroup>
-
 </Project>

src/Microsoft.VisualBasic/tests/UnitTests/Microsoft.VisualBasic.Tests.csproj

@@ -15,5 +15,4 @@
     <ProjectReference Include="..\..\..\System.Windows.Forms.Primitives\tests\TestUtilities\System.Windows.Forms.Primitives.TestUtilities.csproj" />
     <ProjectReference Include="..\..\src\Microsoft.VisualBasic.Facade.csproj" />
   </ItemGroup>
-
 </Project>

src/System.Windows.Forms.Design/tests/UnitTests/System.Windows.Forms.Design.Tests.csproj

@@ -59,5 +59,4 @@
       <HintPath>$(ArtifactsBinDir)\AxHosts\$(Configuration)\net472\Interop.WMPLib.dll</HintPath>
     </Reference>
   </ItemGroup>
-
 </Project>

src/System.Windows.Forms.Primitives/tests/TestUtilities.Tests/System.Windows.Forms.Primitives.TestUtilities.Tests.csproj

@@ -17,5 +17,4 @@
   <ItemGroup>
     <ProjectReference Include="..\TestUtilities\System.Windows.Forms.Primitives.TestUtilities.csproj" />
   </ItemGroup>
-
 </Project>

src/System.Windows.Forms.Primitives/tests/UnitTests/Interop/Mocks/MockCursor.cs

@@ -22,13 +22,9 @@ internal MockCursor(PCWSTR nResourceId)
 
         public void Dispose()
         {
-            if (!_handle.IsNull)
+            if (!_handle.IsNull && _ownHandle)
             {
-                if (_ownHandle)
-                {
-                    PInvoke.DestroyCursor(_handle);
-                }
-
+                PInvoke.DestroyCursor(_handle);
                 _handle = HCURSOR.Null;
             }
         }

src/System.Windows.Forms.Primitives/tests/UnitTests/System.Windows.Forms.Primitives.Tests.csproj

@@ -16,5 +16,4 @@
   <ItemGroup>
     <ProjectReference Include="..\TestUtilities\System.Windows.Forms.Primitives.TestUtilities.csproj" />
   </ItemGroup>
-
 </Project>

src/System.Windows.Forms.Primitives/tests/UnitTests/System/Windows/Forms/LocalAppContextSwitchesTest.cs

@@ -7,7 +7,6 @@
 
 namespace System.Windows.Forms.Tests
 {
-    [Collection(nameof(SynchronousCollection))]
     public class LocalAppContextSwitchesTest
     {
         private void ResetLocalSwitches(dynamic testAccessor)

src/System.Windows.Forms.PrivateSourceGenerators/tests/UnitTests/System.Windows.Forms.PrivateSourceGenerators.Tests.csproj

@@ -15,5 +15,4 @@
   <ItemGroup>
     <ProjectReference Include="..\..\src\System.Windows.Forms.PrivateSourceGenerators.csproj" />
   </ItemGroup>
-
 </Project>

src/System.Windows.Forms/src/Resources/SR.resx

@@ -6961,4 +6961,7 @@ Stack trace where the illegal operation occurred was:
   <data name="InvalidArgumentType" xml:space="preserve">
     <value>Argument '{0}' must be of type '{1}'.</value>
   </data>
-</root>
+  <data name="FailedToLoadCursor" xml:space="preserve">
+    <value>Failed to load cursor. Error '{1}'.</value>
+  </data>
+</root>

src/System.Windows.Forms/src/System/Windows/Forms/Cursor.cs

@@ -23,7 +23,6 @@ namespace System.Windows.Forms
     public sealed class Cursor : IDisposable, ISerializable, IHandle<HICON>, IHandle<HANDLE>
     {
         private static Size s_cursorSize = Size.Empty;
-
         private readonly byte[]? _cursorData;
         private HCURSOR _handle;
         private bool _ownHandle = true;
@@ -39,6 +38,10 @@ internal unsafe Cursor(PCWSTR nResourceId)
             _ownHandle = false;
             _resourceId = nResourceId;
             _handle = PInvoke.LoadCursor((HINSTANCE)0, nResourceId);
+            if (_handle.IsNull)
+            {
+                throw new Win32Exception(string.Format(SR.FailedToLoadCursor, Marshal.GetLastWin32Error()));
+            }
         }
 
         /// <summary>
@@ -145,6 +148,7 @@ public IntPtr Handle
             get
             {
                 ObjectDisposedException.ThrowIf(_handle.IsNull, this);
+
                 return (nint)_handle;
             }
         }
@@ -222,13 +226,9 @@ public void Dispose()
 
         private void Dispose(bool disposing)
         {
-            if (!_handle.IsNull)
+            if (!_handle.IsNull && _ownHandle)
             {
-                if (_ownHandle)
-                {
-                    PInvoke.DestroyCursor(_handle);
-                }
-
+                PInvoke.DestroyCursor(_handle);
                 _handle = HCURSOR.Null;
             }
         }
@@ -430,6 +430,11 @@ private unsafe void LoadPicture(IStream.Interface stream, string paramName)
                         picSize.Height,
                         IMAGE_FLAGS.LR_DEFAULTCOLOR).Value;
 
+                    if (_handle.IsNull)
+                    {
+                        throw new Win32Exception(string.Format(SR.FailedToLoadCursor, Marshal.GetLastWin32Error()));
+                    }
+
                     _ownHandle = true;
                 }
                 else

src/System.Windows.Forms/tests/IntegrationTests/System.Windows.Forms.IntegrationTests/System.Windows.Forms.IntegrationTests.csproj

@@ -8,5 +8,4 @@
     <ProjectReference Include="..\..\..\src\System.Windows.Forms.csproj" />
     <ProjectReference Include="..\WinformsControlsTest\WinformsControlsTest.csproj" />
   </ItemGroup>
-
 </Project>