feat: add test for LineCount.

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

@@ -0,0 +1,72 @@
+using System.Security.Cryptography.X509Certificates;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Controls.Shapes;
+using Avalonia.Headless.XUnit;
+using Avalonia.Layout;
+using Ursa.Controls;
+
+namespace HeadlessTest.Ursa.Controls.ElasticWrapPanelTests;
+
+public class Tests
+{
+    [AvaloniaFact]
+    public void LineCount_Correct()
+    {
+        var window = new Window() { };
+        var panel = new ElasticWrapPanel
+        {
+            Width = 200,
+            Height = 200,
+            Orientation = Orientation.Horizontal,
+        };
+        window.Content = panel;
+        window.Show();
+        Assert.Equal(0, panel.LineCount);
+    }
+    
+    [AvaloniaFact]
+    public void LineCount_Correct_1()
+    {
+        var window = new Window() { };
+        var panel = new ElasticWrapPanel
+        {
+            Width = 200,
+            Height = 200,
+            Orientation = Orientation.Horizontal,
+        };
+        var rect = new Rectangle
+        {
+            Width = 100,
+            Height = 100,
+        };
+        panel.Children.Add(rect);
+        window.Content = panel;
+        window.Show();
+        Assert.Equal(1, panel.LineCount);
+    }
+    
+    [AvaloniaFact]
+    public void LineCount_Correct_2()
+    {
+        var window = new Window() { };
+        var panel = new ElasticWrapPanel
+        {
+            Width = 200,
+            Height = 200,
+            Orientation = Orientation.Horizontal,
+        };
+        for (int i = 0; i < 3; i++)
+        {
+            var rect = new Rectangle
+            {
+                Width = 100,
+                Height = 100,
+            };
+            panel.Children.Add(rect);
+        }
+        window.Content = panel;
+        window.Show();
+        Assert.Equal(2, panel.LineCount);
+    }
+}