Add unit test for GridEntryRecreateChildrenEventArgs.cs file (#13497)

* Add unit test for GridEntryRecreateChildrenEventArgs.cs file

Author: Philip-Wang01

src/test/unit/System.Windows.Forms/System/Windows/Forms/GridEntryRecreateChildrenEventArgsTests.cs

@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Windows.Forms.PropertyGridInternal;
+
+namespace System.Windows.Forms.Tests;
+
+public class GridEntryRecreateChildrenEventArgsTests
+{
+    [Theory]
+    [InlineData(0, 0)]
+    [InlineData(1, 2)]
+    [InlineData(-1, 5)]
+    [InlineData(10, -3)]
+    [InlineData(int.MaxValue, int.MinValue)]
+    [InlineData(int.MinValue, int.MaxValue)]
+    public void GridEntryRecreateChildrenEventArgs_SetsProperties(int oldCount, int newCount)
+    {
+        GridEntryRecreateChildrenEventArgs args = new(oldCount, newCount);
+
+        args.OldChildCount.Should().Be(oldCount);
+        args.NewChildCount.Should().Be(newCount);
+    }
+
+    [Fact]
+    public void GridEntryRecreateChildrenEventArgs_Inherits_EventArgs()
+    {
+        GridEntryRecreateChildrenEventArgs args = new(1, 2);
+
+        args.Should().BeAssignableTo<EventArgs>();
+    }
+}