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/Test.Ursa/AnchorTests/AnchorUnitTests.cs

@@ -0,0 +1,121 @@
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Controls.Primitives;
+using Ursa.Controls;
+
+namespace Test.Ursa.AnchorTests;
+
+public class AnchorUnitTests
+{
+    [Fact]
+    public void Anchor_Properties_Should_Have_Correct_Default_Values()
+    {
+        var anchor = new Anchor();
+        
+        Assert.Null(anchor.TargetContainer);
+        Assert.Equal(0.0, anchor.TopOffset);
+    }
+
+    [Fact]
+    public void Anchor_Should_Set_And_Get_TargetContainer()
+    {
+        var anchor = new Anchor();
+        var scrollViewer = new ScrollViewer();
+        
+        anchor.TargetContainer = scrollViewer;
+        Assert.Equal(scrollViewer, anchor.TargetContainer);
+        
+        anchor.TargetContainer = null;
+        Assert.Null(anchor.TargetContainer);
+    }
+
+    [Fact]
+    public void Anchor_Should_Set_And_Get_TopOffset()
+    {
+        var anchor = new Anchor();
+        
+        anchor.TopOffset = 25.5;
+        Assert.Equal(25.5, anchor.TopOffset);
+        
+        anchor.TopOffset = -10.0;
+        Assert.Equal(-10.0, anchor.TopOffset);
+        
+        anchor.TopOffset = 0.0;
+        Assert.Equal(0.0, anchor.TopOffset);
+    }
+
+    [Fact]
+    public void Anchor_Id_AttachedProperty_Should_Work_With_Different_Visual_Types()
+    {
+        var border = new Border();
+        var textBlock = new TextBlock();
+        var stackPanel = new StackPanel();
+        
+        // Test with Border
+        Anchor.SetId(border, "border-id");
+        Assert.Equal("border-id", Anchor.GetId(border));
+        
+        // Test with TextBlock
+        Anchor.SetId(textBlock, "text-id");
+        Assert.Equal("text-id", Anchor.GetId(textBlock));
+        
+        // Test with StackPanel
+        Anchor.SetId(stackPanel, "panel-id");
+        Assert.Equal("panel-id", Anchor.GetId(stackPanel));
+        
+        // Test setting to null
+        Anchor.SetId(border, null);
+        Assert.Null(Anchor.GetId(border));
+    }
+
+    [Fact]
+    public void AnchorItem_Properties_Should_Have_Correct_Default_Values()
+    {
+        var anchorItem = new AnchorItem();
+        
+        Assert.Null(anchorItem.AnchorId);
+        Assert.False(anchorItem.IsSelected);
+        Assert.Equal(0, anchorItem.Level); // Default level before attachment
+    }
+
+    [Fact]
+    public void AnchorItem_Should_Set_And_Get_AnchorId()
+    {
+        var anchorItem = new AnchorItem();
+        
+        anchorItem.AnchorId = "test-anchor";
+        Assert.Equal("test-anchor", anchorItem.AnchorId);
+        
+        anchorItem.AnchorId = null;
+        Assert.Null(anchorItem.AnchorId);
+        
+        anchorItem.AnchorId = "";
+        Assert.Equal("", anchorItem.AnchorId);
+    }
+
+    [Fact]
+    public void AnchorItem_Should_Set_And_Get_IsSelected()
+    {
+        var anchorItem = new AnchorItem();
+        
+        anchorItem.IsSelected = true;
+        Assert.True(anchorItem.IsSelected);
+        
+        anchorItem.IsSelected = false;
+        Assert.False(anchorItem.IsSelected);
+    }
+
+    [Fact]
+    public void Anchor_Should_Create_AnchorItem_Containers()
+    {
+        var anchor = new Anchor();
+        
+        // Test NeedsContainer
+        var needsContainer = anchor.NeedsContainerOverrideInternal("test-item", 0, out var recycleKey);
+        Assert.True(needsContainer);
+        
+        // Test CreateContainer
+        var container = anchor.CreateContainerForItemOverrideInternal("test-item", 0, recycleKey);
+        Assert.IsType<AnchorItem>(container);
+    }
+}