Add comprehensive test coverage for many controls (#737)

Co-authored-by: rabbitism <14807942+rabbitism@users.noreply.github.com>
Co-authored-by: Copilot <198982749+Copilot@users.noreply.github.com>

tests/HeadlessTest.Ursa/Controls/AnchorTests/Tests.cs

@@ -92,6 +92,184 @@ public class Tests
         var items = window.GetVisualDescendants().OfType<AnchorItem>().ToList();
         Assert.NotEmpty(items);
         Assert.Equal(10, items.Count);
+    }
 
+    [AvaloniaFact]
+    public void TopOffset_Property_Should_Affect_Scroll_Position()
+    {
+        var window = new Window()
+        {
+            Width = 500,
+            Height = 500,
+        };
+        var view = new TestView();
+        window.Content = view;
+        window.Show();
+        
+        var anchor = view.FindControl<Anchor>("Anchor");
+        var scrollViewer = view.FindControl<ScrollViewer>("ScrollViewer");
+        
+        Assert.NotNull(anchor);
+        Assert.NotNull(scrollViewer);
+        
+        // Set TopOffset to 50
+        anchor.TopOffset = 50;
+        
+        // Scroll to position that should trigger item2 selection
+        scrollViewer.Offset = new Vector(0, 310.0);
+        Dispatcher.UIThread.RunJobs();
+        
+        // Check that the offset affects position calculations
+        Assert.Equal(50, anchor.TopOffset);
+        
+        // The behavior should account for the top offset
+        anchor.InvalidatePositions();
+        Dispatcher.UIThread.RunJobs();
+    }
+
+    [AvaloniaFact]
+    public void InvalidatePositions_Should_Update_Internal_Positions()
+    {
+        var window = new Window()
+        {
+            Width = 500,
+            Height = 500,
+        };
+        var view = new TestView();
+        window.Content = view;
+        window.Show();
+        
+        var anchor = view.FindControl<Anchor>("Anchor");
+        var scrollViewer = view.FindControl<ScrollViewer>("ScrollViewer");
+        
+        Assert.NotNull(anchor);
+        Assert.NotNull(scrollViewer);
+        
+        Dispatcher.UIThread.RunJobs();
+        
+        // Call InvalidatePositions explicitly
+        anchor.InvalidatePositions();
+        Dispatcher.UIThread.RunJobs();
+        
+        // Verify that positions are correctly calculated by checking selection
+        var item1 = view.FindControl<AnchorItem>("Item1");
+        Assert.NotNull(item1);
+        Assert.True(item1.IsSelected); // Should be selected at top
+    }
+
+    [AvaloniaFact]
+    public void Anchor_Id_Attached_Property_Should_Work()
+    {
+        var border = new Border();
+        
+        // Test SetId and GetId
+        Anchor.SetId(border, "test-id");
+        var retrievedId = Anchor.GetId(border);
+        
+        Assert.Equal("test-id", retrievedId);
+        
+        // Test with null
+        Anchor.SetId(border, null);
+        var nullId = Anchor.GetId(border);
+        Assert.Null(nullId);
+    }
+
+    [AvaloniaFact]
+    public void Anchor_Without_TargetContainer_Should_Not_Crash()
+    {
+        var window = new Window();
+        var anchor = new Anchor();
+        window.Content = anchor;
+        window.Show();
+        
+        // These operations should not crash when TargetContainer is null
+        anchor.InvalidatePositions();
+        Dispatcher.UIThread.RunJobs();
+        
+        // Should not throw
+        Assert.Null(anchor.TargetContainer);
+    }
+
+    [AvaloniaFact]
+    public void AnchorItem_Level_Property_Should_Calculate_Correctly()
+    {
+        var window = new Window()
+        {
+            Width = 500,
+            Height = 500,
+        };
+        var view = new TestView();
+        window.Content = view;
+        window.Show();
+        
+        Dispatcher.UIThread.RunJobs();
+        
+        var item1 = view.FindControl<AnchorItem>("Item1");
+        var item2 = view.FindControl<AnchorItem>("Item2");
+        var item4 = view.FindControl<AnchorItem>("Item4");
+        
+        Assert.NotNull(item1);
+        Assert.NotNull(item2);
+        Assert.NotNull(item4);
+        
+        // Based on the XAML structure, Item1 is inside Anchor (level 1)
+        Assert.Equal(1, item1.Level);
+        
+        // Item2 is nested inside Item1, so level 2
+        Assert.Equal(2, item2.Level);
+        
+        // Item4 is at the same level as Item1
+        Assert.Equal(1, item4.Level);
+    }
+
+    [AvaloniaFact]
+    public void AnchorItem_Without_Anchor_Parent_Should_Throw()
+    {
+        // This test verifies that AnchorItem throws when not inside an Anchor
+        var anchorItem = new AnchorItem();
+        var window = new Window();
+        
+        // Add some items to the AnchorItem to trigger container creation
+        anchorItem.ItemsSource = new[] { "Item1", "Item2" };
+        window.Content = anchorItem;
+        
+        // The exception should be thrown when showing the window
+        var exception = Assert.Throws<InvalidOperationException>(() => window.Show());
+        Assert.Contains("AnchorItem must be inside an Anchor control", exception.Message);
+    }
+
+    [AvaloniaFact]
+    public async void Scroll_To_Bottom_Should_Handle_Edge_Case()
+    {
+        var window = new Window()
+        {
+            Width = 500,
+            Height = 500,
+        };
+        var view = new TestView();
+        window.Content = view;
+        window.Show();
+        
+        var anchor = view.FindControl<Anchor>("Anchor");
+        var scrollViewer = view.FindControl<ScrollViewer>("ScrollViewer");
+        
+        Assert.NotNull(anchor);
+        Assert.NotNull(scrollViewer);
+        
+        Dispatcher.UIThread.RunJobs();
+        
+        // Scroll to the very bottom
+        var maxOffset = scrollViewer.Extent.Height - scrollViewer.Bounds.Height;
+        scrollViewer.Offset = new Vector(0, maxOffset);
+        Dispatcher.UIThread.RunJobs();
+        
+        // Should handle the edge case without crashing
+        anchor.InvalidatePositions();
+        Dispatcher.UIThread.RunJobs();
+        
+        // The last item should be selected
+        var lastItems = window.GetVisualDescendants().OfType<AnchorItem>()
+            .Where(i => i.IsSelected).ToList();
+        Assert.Single(lastItems);
     }
 }