test: add failing test case for issue 460.

tests/HeadlessTest.Ursa/Controls/UrsaWindowTests/UrsaWindowTest.cs

@@ -0,0 +1,44 @@
+using Avalonia.Headless.XUnit;
+using Ursa.Controls;
+
+namespace HeadlessTest.Ursa.Controls.UrsaWindowTests;
+
+public class UrsaWindowTest
+{
+    [AvaloniaFact]
+    public void Default_UrsaWindow_Closing_Is_Called_Once()
+    {
+        var ursaWindow = new UrsaWindow();
+        ursaWindow.Show();
+        int count = 0;
+        ursaWindow.Closing += (_, _) => count++;
+        ursaWindow.Close();
+        Assert.Equal(1, count);
+    }
+
+    [AvaloniaFact]
+    public async void Inferenced_Window_Closing_Called_Once_When_Yes()
+    {
+        var window = new UrsaWindowWithCloseInference();
+        window.Show();
+        int count = 0;
+        window.Closing += (_, _) => count++;
+        window.Close();
+        window.DialogViewModel.CloseYes();
+        Assert.Equal(1, count);
+    }
+
+    [AvaloniaFact]
+    public async void Inferenced_Window_Closing_Called_Once_When_No()
+    {
+        var window = new UrsaWindowWithCloseInference();
+        window.Show();
+        int count = 0;
+        window.Closing += (_, _) => count++;
+        window.Close();
+        window.DialogViewModel.Close();
+        Assert.Equal(1, count);
+    }
+    
+    
+}