Add code coverage for StandardCommandToolStripMenuItem (#13215)

Related #10773

Proposed changes
Add unit test file: StandardCommandToolStripMenuItemTests.cs for public methods of the StandardCommandToolStripMenuItem.cs

Author: Zheng-Li01

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

@@ -0,0 +1,96 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.ComponentModel.Design;
+using System.Drawing;
+using Moq;
+
+namespace System.Windows.Forms.Design.Tests;
+
+public class StandardCommandToolStripMenuItemTests : IDisposable
+{
+    private readonly Mock<IServiceProvider> _serviceProviderMock;
+    private readonly Mock<IMenuCommandService> _menuCommandServiceMock;
+    private readonly CommandID _commandID;
+    private readonly MenuCommand _menuCommand;
+    private readonly StandardCommandToolStripMenuItem _item;
+
+    public StandardCommandToolStripMenuItemTests()
+    {
+        _serviceProviderMock = new();
+        _menuCommandServiceMock = new();
+        _commandID = new(Guid.NewGuid(), 1);
+        _menuCommand = new((sender, e) => { }, _commandID);
+
+        _serviceProviderMock.Setup(sp => sp.GetService(typeof(IMenuCommandService)))
+            .Returns(_menuCommandServiceMock.Object);
+        _menuCommandServiceMock.Setup(mcs => mcs.FindCommand(_commandID))
+            .Returns(_menuCommand);
+
+        _item = new(_commandID, "Test Text", "TestImage", _serviceProviderMock.Object);
+    }
+
+    public void Dispose() => _item.Dispose();
+
+    [WinFormsFact]
+    public void Constructor_InitializesPropertiesCorrectly()
+    {
+        _item.MenuService?.FindCommand(_commandID)?.CommandID.Should().Be(_commandID);
+        string name = _item.TestAccessor().Dynamic._name;
+
+        _item.Text.Should().Be("Test Text");
+        name.Should().BeSameAs("TestImage");
+    }
+
+    [WinFormsFact]
+    public void RefreshItem_UpdatesProperties()
+    {
+        _menuCommand.Visible = false;
+        _menuCommand.Enabled = false;
+        _menuCommand.Checked = true;
+
+        _item.RefreshItem();
+
+        _item.Visible.Should().BeFalse();
+        _item.Enabled.Should().BeFalse();
+        _item.Checked.Should().BeTrue();
+    }
+
+    [WinFormsFact]
+    public void MenuService_RetrievesMenuCommandService()
+    {
+        IMenuCommandService? menuService = _item.MenuService;
+
+        menuService.Should().Be(_menuCommandServiceMock.Object);
+    }
+
+    [WinFormsFact]
+    public void Image_ReturnsCachedImageOnSubsequentAccesses()
+    {
+        Image? firstAccessImage = _item.Image;
+        Image? secondAccessImage = _item.Image;
+
+        firstAccessImage.Should().BeSameAs(secondAccessImage);
+    }
+
+    [WinFormsFact]
+    public void Item_OnClick_WithNullMenuCommand()
+    {
+        Action action = _item.PerformClick;
+        action.Should().NotThrow();
+    }
+
+    [WinFormsFact]
+    public void OnClick_InvokesGlobalCommand_WhenMenuCommandIsNull()
+    {
+        _menuCommandServiceMock.Setup(mcs => mcs.FindCommand(_commandID))
+            .Returns((MenuCommand?)null);
+        _menuCommandServiceMock.Setup(mcs => mcs.GlobalInvoke(_commandID))
+            .Returns(true);
+
+        StandardCommandToolStripMenuItem item = new(_commandID, "Test Text", "TestImage", _serviceProviderMock.Object);
+        item.PerformClick();
+
+        _menuCommandServiceMock.Verify(mcs => mcs.GlobalInvoke(_commandID), Times.Once);
+    }
+}