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/ButtonGroupTests/ButtonGroupTests.cs

@@ -0,0 +1,67 @@
+using Avalonia.Data;
+using Ursa.Controls;
+
+namespace Test.Ursa.ButtonGroupTests;
+
+public class ButtonGroupTests
+{
+    [Fact]
+    public void ButtonGroup_Should_Initialize_With_Default_Values()
+    {
+        var buttonGroup = new ButtonGroup();
+        
+        Assert.Null(buttonGroup.CommandBinding);
+        Assert.Null(buttonGroup.CommandParameterBinding);
+        Assert.Null(buttonGroup.ContentBinding);
+        Assert.NotNull(buttonGroup.Items);
+        Assert.Empty(buttonGroup.Items);
+    }
+
+    [Fact]
+    public void ButtonGroup_Should_Set_And_Get_CommandBinding()
+    {
+        var buttonGroup = new ButtonGroup();
+        var binding = new Binding("TestCommand");
+        
+        buttonGroup.CommandBinding = binding;
+        
+        Assert.Equal(binding, buttonGroup.CommandBinding);
+    }
+
+    [Fact]
+    public void ButtonGroup_Should_Set_And_Get_CommandParameterBinding()
+    {
+        var buttonGroup = new ButtonGroup();
+        var binding = new Binding("TestParameter");
+        
+        buttonGroup.CommandParameterBinding = binding;
+        
+        Assert.Equal(binding, buttonGroup.CommandParameterBinding);
+    }
+
+    [Fact]
+    public void ButtonGroup_Should_Set_And_Get_ContentBinding()
+    {
+        var buttonGroup = new ButtonGroup();
+        var binding = new Binding("TestContent");
+        
+        buttonGroup.ContentBinding = binding;
+        
+        Assert.Equal(binding, buttonGroup.ContentBinding);
+    }
+
+    [Fact]
+    public void ButtonGroup_Should_Accept_Items_In_Collection()
+    {
+        var buttonGroup = new ButtonGroup();
+        var item1 = "Item 1";
+        var item2 = new Avalonia.Controls.Button { Content = "Button Item" };
+        
+        buttonGroup.Items.Add(item1);
+        buttonGroup.Items.Add(item2);
+        
+        Assert.Equal(2, buttonGroup.Items.Count);
+        Assert.Contains(item1, buttonGroup.Items);
+        Assert.Contains(item2, buttonGroup.Items);
+    }
+}