Add AccessKeyHandler tests for accelerators with more than one match

Author: hdocsek

tests/Avalonia.Base.UnitTests/Input/AccessKeyHandlerTests.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using Avalonia.Controls;
+using Avalonia.Controls.Primitives;
 using Avalonia.Input;
 using Avalonia.UnitTests;
 using Moq;
@@ -206,6 +207,56 @@ public void Should_Open_MainMenu_On_Alt_KeyUp()
             menu.Verify(x => x.Open(), Times.Once);
         }
 
+        [Fact]
+        public void Should_Cycle_Focus_When_Accelerator_Has_More_Than_One_Match()
+        {
+            using (UnitTestApplication.Start(TestServices.RealFocus))
+            {
+                var fileMenuItem = new MenuItem{ Header = "_File", Focusable = true, IsVisible = true };
+                var fileItemAccessText = new AccessText { Text = "_File" };
+                fileMenuItem.AddLogicalChild(fileItemAccessText);
+                
+                var findItemAccessText = new AccessText { Text = "_Find" };
+                var findItem = new MenuItem{ Header = "_Find" ,Focusable = true, IsVisible = true };
+                findItem.AddLogicalChild(findItemAccessText);
+                
+                var root = new TestRoot
+                {
+                    Child = new StackPanel
+                    {
+                        Children =
+                        {
+                            findItem,
+                            fileMenuItem
+                        }
+                    }
+                };
+                
+                var target = new AccessKeyHandler();
+                
+                target.SetOwner(root);
+                var focusManager = Assert.IsType<FocusManager>(root.FocusManager);
+                
+                target.Register('F', fileItemAccessText);
+                target.Register('F', findItemAccessText);
+                
+                // focus first item
+                KeyDown(root, Key.F, KeyModifiers.Alt);
+                var focusedElement = Assert.IsType<MenuItem>(focusManager.GetFocusedElement());
+                Assert.Same(fileMenuItem.Header, focusedElement.Header);
+                
+                // focus next item
+                KeyDown(root, Key.F, KeyModifiers.Alt);
+                focusedElement = Assert.IsType<MenuItem>(focusManager.GetFocusedElement());
+                Assert.Same(findItem.Header, focusedElement.Header);
+                
+                // focus first item again
+                KeyDown(root, Key.F, KeyModifiers.Alt);
+                focusedElement = Assert.IsType<MenuItem>(focusManager.GetFocusedElement());
+                Assert.Same(fileMenuItem.Header, focusedElement.Header);
+            }
+        }
+
         private static void KeyDown(IInputElement target, Key key, KeyModifiers modifiers = KeyModifiers.None)
         {
             target.RaiseEvent(new KeyEventArgs