Add unit tests for PictureBoxActionList

src/System.Windows.Forms.Design/tests/UnitTests/System/Windows/Forms/Design/PictureBoxActionListTests.cs

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+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#nullable enable
+
+using System.ComponentModel.Design;
+
+namespace System.Windows.Forms.Design.Tests;
+
+public sealed class PictureBoxActionListTests
+{
+    [Fact]
+    public void SizeMode_ShouldReturnCorrectValue()
+    {
+        using PictureBox pictureBox = new() { SizeMode = PictureBoxSizeMode.StretchImage };
+        using PictureBoxDesigner designer = new();
+        designer.Initialize(pictureBox);
+        PictureBoxActionList actionList = new(designer);
+
+        actionList.SizeMode.Should().Be(PictureBoxSizeMode.StretchImage);
+    }
+
+    [Fact]
+    public void SizeMode_ShouldUpdateCorrectly()
+    {
+        using PictureBox pictureBox = new();
+        using PictureBoxDesigner designer = new();
+        designer.Initialize(pictureBox);
+        PictureBoxActionList actionList = new(designer)
+        {
+            SizeMode = PictureBoxSizeMode.Zoom
+        };
+
+        pictureBox.SizeMode.Should().Be(PictureBoxSizeMode.Zoom);
+    }
+
+    [Fact]
+    public void GetSortedActionItems_ShouldReturnCorrectItems()
+    {
+        using PictureBox pictureBox = new();
+        using PictureBoxDesigner designer = new();
+        designer.Initialize(pictureBox);
+        PictureBoxActionList actionList = new(designer);
+
+        DesignerActionItemCollection items = actionList.GetSortedActionItems();
+
+        items.Should().NotBeNull();
+        items.Count.Should().Be(2);
+        items[0].Should().BeOfType<DesignerActionMethodItem>();
+        items[1].Should().BeOfType<DesignerActionPropertyItem>();
+
+        var methodItem = items[0].As<DesignerActionMethodItem>();
+        methodItem.MemberName.Should().Be("ChooseImage");
+
+        var propertyItem = items[1].As<DesignerActionPropertyItem>();
+        propertyItem.MemberName.Should().Be("SizeMode");
+    }
+}
+