Fix exception dialog handling. (#8695)

Test fixtures do not run on the same thread the test method executes on when marked with `[WinFormsFact]` or `[StaFact]`. This change removes the test fixture and adds a new context switch to throw thread exceptions.

Initialization of the switch is done programmatically via a module initializer. The module initializer will also set the starting cursor position to avoid spurious errors in tests due to cursor positioning.

The Cursor tests were the ones modifying the cursor position and causing intermittent errors in other tests. Moved them to their own collection and forced them to run sequentially.

Cleaned up WindowsFormsSynchronizationContext.

Simplified checks in LocalAppContextSwitches. We shouldn't be conditioning on supported OS beyond checking for UI availability. We don't support Windows 7, but we won't deliberately cause WinForms apps to crash on Windows by calling later APIs without checking for support. We will not add additional complexity to the code beyond that for unsupported OS platforms.

Author: JeremyKuhne

docs/testing.md

@@ -6,7 +6,7 @@ Imports System.Windows.Forms
 Imports Xunit
 
 Namespace Microsoft.VisualBasic.Forms.Tests
-    Partial Public Class ControlTests : Implements IClassFixture(Of ThreadExceptionFixture)
+    Partial Public Class ControlTests
 
         <WinFormsFact>
         Public Sub Control_Invoke_Action_calls_correct_method()

src/Microsoft.VisualBasic.Forms/tests/UnitTests/System/Windows/Forms/ControlTests.vb

@@ -8,7 +8,7 @@
 
 namespace System.Windows.Forms.Design.Tests
 {
-    public class ControlDesignerTests : IClassFixture<ThreadExceptionFixture>
+    public class ControlDesignerTests
     {
         [Fact]
         public void AccessibleObjectField()

src/System.Windows.Forms.Design/tests/UnitTests/ControlDesignerTests.cs

@@ -7,7 +7,7 @@
 
 namespace System.Windows.Forms.Design.Editors.Tests
 {
-    public class EnsureDesignerTests : IClassFixture<ThreadExceptionFixture>
+    public class EnsureDesignerTests
     {
         [WinFormsFact]
         public void Ensure_designer_type_forwarded()

src/System.Windows.Forms.Design/tests/UnitTests/EnsureDesignerTests.cs

@@ -13,7 +13,7 @@
 
 namespace System.Windows.Forms.Design.Editors.Tests
 {
-    public class EnsureEditorsTests : IClassFixture<ThreadExceptionFixture>
+    public class EnsureEditorsTests
     {
         [WinFormsFact]
         public void Ensure_editors_type_forwarded()

src/System.Windows.Forms.Design/tests/UnitTests/EnsureEditorsTests.cs

@@ -6,7 +6,7 @@
 
 namespace System.Windows.Forms.Design.Tests.Serialization
 {
-    public class SerializableAttributeTests : IClassFixture<ThreadExceptionFixture>
+    public class SerializableAttributeTests
     {
         [Fact]
         public void EnsureSerializableAttribute()

src/System.Windows.Forms.Design/tests/UnitTests/SerializableAttributeTests.cs

@@ -10,7 +10,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class ArrayEditorTests : IClassFixture<ThreadExceptionFixture>
+    public class ArrayEditorTests
     {
         [Theory]
         [InlineData(typeof(object), null)]

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/ArrayEditorTests.cs

@@ -11,7 +11,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class ByteViewerTests : IClassFixture<ThreadExceptionFixture>
+    public class ByteViewerTests
     {
         [WinFormsFact]
         public void ByteViewer_Ctor_Default()

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/ByteViewerTests.cs

@@ -14,7 +14,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class CollectionEditorTests : IClassFixture<ThreadExceptionFixture>
+    public class CollectionEditorTests
     {
         [Theory]
         [InlineData(typeof(object), typeof(object))]

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/CollectionEditorTests.cs

@@ -10,7 +10,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class CollectionFormTests : CollectionEditor, IClassFixture<ThreadExceptionFixture>
+    public class CollectionFormTests : CollectionEditor
     {
         public CollectionFormTests() : base(typeof(List<int>))
         {

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/CollectionFormTests.cs

@@ -11,7 +11,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class ComponentDesignerTests : IClassFixture<ThreadExceptionFixture>
+    public class ComponentDesignerTests
     {
         [Fact]
         public void ComponentDesigner_Ctor_Default()

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/ComponentDesignerTests.cs

@@ -11,7 +11,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class DesignSurfaceTests : IClassFixture<ThreadExceptionFixture>
+    public class DesignSurfaceTests
     {
         [WinFormsFact]
         public void DesignSurface_Ctor_Default()

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignSurfaceTests.cs

@@ -7,7 +7,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class DesignerActionHeaderItemTests : IClassFixture<ThreadExceptionFixture>
+    public class DesignerActionHeaderItemTests
     {
         [Theory]
         [InlineData("displayName", "category", "displayName")]

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignerActionHeaderItemTests.cs

@@ -6,7 +6,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class DesignerActionItemCollectionTests : IClassFixture<ThreadExceptionFixture>
+    public class DesignerActionItemCollectionTests
     {
         [Fact]
         public void DesignerActionItemCollection_Ctor_Default()

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignerActionItemCollectionTests.cs

@@ -8,7 +8,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class DesignerActionItemTests : IClassFixture<ThreadExceptionFixture>
+    public class DesignerActionItemTests
     {
         [Theory]
         [InlineData("displayName", "category", "description", "displayName")]

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignerActionItemTests.cs

@@ -6,7 +6,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class DesignerActionListCollectionTests : IClassFixture<ThreadExceptionFixture>
+    public class DesignerActionListCollectionTests
     {
         [Fact]
         public void DesignerActionListCollection_Ctor_Default()

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignerActionListCollectionTests.cs

@@ -9,7 +9,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class DesignerActionListTests : IClassFixture<ThreadExceptionFixture>
+    public class DesignerActionListTests
     {
         public static IEnumerable<object[]> Ctor_IComponent_TestDat()
         {

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignerActionListTests.cs

@@ -6,7 +6,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class DesignerActionListsChangedEventArgsTests : IClassFixture<ThreadExceptionFixture>
+    public class DesignerActionListsChangedEventArgsTests
     {
         public static IEnumerable<object[]> Ctor_Object_DesignerActionListsChangedType_DesignerActionListCollection_TestData()
         {

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignerActionListsChangedEventArgsTests.cs

@@ -8,7 +8,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class DesignerActionMethodItemTests : IClassFixture<ThreadExceptionFixture>
+    public class DesignerActionMethodItemTests
     {
         public static IEnumerable<object[]> Ctor_DesignerActionList_String_String_String_String_Bool_TestData()
         {

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignerActionMethodItemTests.cs

@@ -7,7 +7,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class DesignerActionPropertyItemTests : IClassFixture<ThreadExceptionFixture>
+    public class DesignerActionPropertyItemTests
     {
         [Theory]
         [InlineData("memberName", "displayName", "category", "description", "displayName")]

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignerActionPropertyItemTests.cs

@@ -11,7 +11,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class DesignerActionServiceTests : IClassFixture<ThreadExceptionFixture>
+    public class DesignerActionServiceTests
     {
         [Fact]
         public void Ctor_IServiceProvider()

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignerActionServiceTests.cs

@@ -7,7 +7,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class DesignerActionTextItemTests : IClassFixture<ThreadExceptionFixture>
+    public class DesignerActionTextItemTests
     {
         [Theory]
         [InlineData("displayName", "category", "displayName")]

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignerActionTextItemTests.cs

@@ -6,7 +6,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class DesignerActionUIStateChangeEventArgsTests : IClassFixture<ThreadExceptionFixture>
+    public class DesignerActionUIStateChangeEventArgsTests
     {
         public static IEnumerable<object[]> Ctor_Object_DesignerActionUIStateChangeType_TestData()
         {

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignerActionUIStateChangeEventArgsTests.cs

@@ -8,7 +8,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class DesignerCommandSetTests : IClassFixture<ThreadExceptionFixture>
+    public class DesignerCommandSetTests
     {
         [Fact]
         public void DesignerCommandSet_Ctor_Default()

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignerCommandSetTests.cs

@@ -11,7 +11,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class DesignerHostTests : IClassFixture<ThreadExceptionFixture>
+    public class DesignerHostTests
     {
         [WinFormsTheory]
         [CommonMemberData(typeof(CommonTestHelper), nameof(CommonTestHelper.GetBoolTheoryData))]

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignerHostTests.cs

@@ -9,7 +9,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class ExceptionCollectionTests : IClassFixture<ThreadExceptionFixture>
+    public class ExceptionCollectionTests
     {
         public static IEnumerable<object[]> Ctor_ArrayList_TestData()
         {

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/ExceptionCollectionTests.cs

@@ -7,7 +7,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class ExtenderProviderServiceTests : IClassFixture<ThreadExceptionFixture>
+    public class ExtenderProviderServiceTests
     {
         [Fact]
         public void ExtenderProviderService_GetExtenderProviders_Invoke_ReturnsEmpty()

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/ExtenderProviderServiceTests.cs

@@ -6,7 +6,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class InheritanceServicerTests : IClassFixture<ThreadExceptionFixture>
+    public class InheritanceServicerTests
     {
         [Fact]
         public void InheritanceService_Constructor()

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/InheritanceServiceTests.cs

@@ -7,7 +7,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class LoadedEventArgsTests : IClassFixture<ThreadExceptionFixture>
+    public class LoadedEventArgsTests
     {
         public static IEnumerable<object[]> Ctor_Bool_ICollection_TestData()
         {

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/LoadedEventArgsTests.cs

@@ -11,7 +11,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class MultilineStringEditorTests : IClassFixture<ThreadExceptionFixture>
+    public class MultilineStringEditorTests
     {
         [Fact]
         public void MultilineStringEditor_Ctor_Default()

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/MultilineStringEditorTests.cs

@@ -11,7 +11,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class ObjectSelectorEditorTests : IClassFixture<ThreadExceptionFixture>
+    public class ObjectSelectorEditorTests
     {
         [Fact]
         public void ObjectSelectorEditor_Ctor_Default()

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/ObjectSelectorEditorTests.cs

@@ -7,7 +7,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class ProjectTargetFrameworkAttributeTests : IClassFixture<ThreadExceptionFixture>
+    public class ProjectTargetFrameworkAttributeTests
     {
         [Theory]
         [CommonMemberData(typeof(CommonTestHelper), nameof(CommonTestHelper.GetStringWithNullTheoryData))]

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/ProjectTargetFrameworkAttributeTests.cs

@@ -14,7 +14,7 @@
 
 namespace System.ComponentModel.Design.Serialization.Tests
 {
-    public class CodeDomComponentSerializationServiceTests : IClassFixture<ThreadExceptionFixture>
+    public class CodeDomComponentSerializationServiceTests
     {
         private Mock<ISite> GetDefaultMockSite(string name)
         {

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/Serialization/CodeDomComponentSerializationServiceTests.cs

@@ -11,7 +11,7 @@
 
 namespace System.Windows.Forms.Design.Serialization.Tests
 {
-    public class CodeDomSerializerExceptionTests : IClassFixture<ThreadExceptionFixture>
+    public class CodeDomSerializerExceptionTests
     {
         public static IEnumerable<object[]> Ctor_String_CodeLinePragma_TestData()
         {

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/Serialization/CodeDomSerializerExceptionTests.cs

@@ -10,7 +10,7 @@
 
 namespace System.ComponentModel.Design.Serialization.Tests
 {
-    public class DesignerSerializationManagerTests : IClassFixture<ThreadExceptionFixture>
+    public class DesignerSerializationManagerTests
     {
         [Fact]
         public void DesignerSerializationManager_Ctor_Default()

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/Serialization/DesignerSerializationManagerTests.cs

@@ -7,7 +7,7 @@
 
 namespace System.ComponentModel.Design.Serialization.Tests
 {
-    public class ExpressionContextTests : IClassFixture<ThreadExceptionFixture>
+    public class ExpressionContextTests
     {
         public static IEnumerable<object[]> Ctor_CodeExpression_Type_Object_Object_TestData()
         {

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/Serialization/ExpressionContextTests.cs

@@ -7,7 +7,7 @@
 
 namespace System.ComponentModel.Design.Serialization.Tests
 {
-    public class RootContextTests : IClassFixture<ThreadExceptionFixture>
+    public class RootContextTests
     {
         [Fact]
         public void RootContext_Ctor_CodeExpression_Object()

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/Serialization/RootContextTests.cs

@@ -6,7 +6,7 @@
 
 namespace System.ComponentModel.Design.Serialization.Tests
 {
-    public class SerializeAbsoluteContextTests : IClassFixture<ThreadExceptionFixture>
+    public class SerializeAbsoluteContextTests
     {
         [Fact]
         public void SerializeAbsoluteContext_Ctor_Default()

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/Serialization/SerializeAbsoluteContextTests.cs

@@ -6,7 +6,7 @@
 
 namespace System.ComponentModel.Design.Serialization.Tests
 {
-    public class StatementContextTests : IClassFixture<ThreadExceptionFixture>
+    public class StatementContextTests
     {
         [Fact]
         public void StatementContext_Ctor_Default()

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/Serialization/StatementContextTests.cs

@@ -8,7 +8,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class SiteNestedContainerTests : IClassFixture<ThreadExceptionFixture>
+    public class SiteNestedContainerTests
     {
         public static IEnumerable<object[]> CreateNestedContainer_TestData()
         {

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/SiteNestedContainerTests.cs

@@ -9,7 +9,7 @@
 
 namespace System.ComponentModel.Design.Tests
 {
-    public class UndoUnitTests : UndoEngine, IClassFixture<ThreadExceptionFixture>
+    public class UndoUnitTests : UndoEngine
     {
         public UndoUnitTests() : base(GetServiceProvider())
         {

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/UndoUnitTests.cs

@@ -9,7 +9,7 @@
 
 namespace System.Drawing.Design.Tests
 {
-    public class BitmapEditorTests : IClassFixture<ThreadExceptionFixture>
+    public class BitmapEditorTests
     {
         [Fact]
         public void BitmapEditor_Ctor_Default()

src/System.Windows.Forms.Design/tests/UnitTests/System/Drawing/Design/BitmapEditorTests.cs

@@ -9,7 +9,7 @@
 
 namespace System.Drawing.Design.Tests
 {
-    public partial class ColorEditor_CustomColorDialogTests : IClassFixture<ThreadExceptionFixture>
+    public partial class ColorEditor_CustomColorDialogTests
     {
         [WinFormsFact]
         public void CustomColorDialog_Ctor_Default()