Add switch to test project

src/System.Windows.Forms/tests/TestUtilities/NotifyUIAProviderTheRichTextContent.cs

@@ -0,0 +1,38 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Windows.Forms.Primitives;
+
+namespace System;
+
+/// <summary>
+///  Scope for enabling / disabling the NotifyUIAProviderTheText Switch.
+/// </summary>
+public readonly ref struct NotifyUIAProviderTheRichTextContent
+{
+    private readonly AppContextSwitchScope _switchScope;
+
+    public NotifyUIAProviderTheRichTextContent(bool enable)
+    {
+        // Prevent multiple NotifyUIAProviderTheRichTextContent from running simultaneously. Using Monitor to allow recursion on
+        // the same thread.
+        Monitor.Enter(typeof(NotifyUIAProviderTheRichTextContent));
+        _switchScope = new(WinFormsAppContextSwitchNames.NotifyUIAProviderTheText, GetDefaultValue, enable);
+    }
+
+    public void Dispose()
+    {
+        try
+        {
+            _switchScope.Dispose();
+        }
+        finally
+        {
+            Monitor.Exit(typeof(NotifyUIAProviderTheRichTextContent));
+        }
+    }
+
+    public static bool GetDefaultValue() =>
+        typeof(LocalAppContextSwitches).TestAccessor()
+            .CreateDelegate<Func<string, bool>>("GetSwitchDefaultValue")(WinFormsAppContextSwitchNames.NotifyUIAProviderTheText);
+}

src/System.Windows.Forms/tests/TestUtilities/WinFormsAppContextSwitchNames.cs

@@ -50,4 +50,10 @@ public const string ServicePointManagerCheckCrl
     /// </summary>
     public const string TreeNodeCollectionAddRangeRespectsSortOrder
         = "System.Windows.Forms.TreeNodeCollectionAddRangeRespectsSortOrder";
+
+    /// <summary>
+    ///  The switch that controls whether the text of the <see cref="Windows.Forms.RichTextBox" /> is sent to the UIA provider.
+    /// </summary>
+    public const string NotifyUIAProviderTheText
+        = "System.Windows.Forms.RichTextBox.NotifyUIAProviderTheText";
 }

src/System.Windows.Forms/tests/UnitTests/System/Windows/Forms/RichTextBoxTests.cs

@@ -10594,6 +10594,7 @@ public void RichTextBox_CheckRichEditWithVersionCanCreateOldVersions()
     [NewAndDefaultData<EventArgs>]
     public void RichTextBox_OnGotFocus_RaisesAutomationNotification_WithText(EventArgs eventArgs)
     {
+        using NotifyUIAProviderTheRichTextContent scope = new(enable: true);
         Mock<Control> mockParent = new() { CallBase = true };
         Mock<Control.ControlAccessibleObject> mockAccessibleObject = new(MockBehavior.Strict, mockParent.Object);
         mockAccessibleObject