Add code coverage for ListViewGroupCollectionEditor

Author: Zheng-Li01

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

@@ -0,0 +1,70 @@
+// 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;
+using System.Reflection;
+using Moq;
+
+namespace System.Windows.Forms.Design.Tests;
+
+public class ListViewGroupCollectionEditorTests
+{
+    private readonly Mock<ListViewGroupCollectionEditor> _mockEditor;
+
+    public ListViewGroupCollectionEditorTests()
+    {
+        _mockEditor = new(typeof(ListViewGroup)) { CallBase = true };
+    }
+
+    [Fact]
+    public void Constructor_InitializesCollectionType()
+    {
+        Type expectedType = typeof(ListViewGroup);
+
+        ListViewGroupCollectionEditor editor = new(expectedType);
+
+        Type actualType = editor.TestAccessor().Dynamic.CollectionType;
+
+        actualType.Should().Be(expectedType);
+    }
+
+    [Fact]
+    public void EditValue_SetsAndResetsEditValue()
+    {
+        Mock<ITypeDescriptorContext> mockContext = new();
+        Mock<IServiceProvider> mockProvider = new();
+        object inputValue = new();
+        object expectedResult = new();
+
+        _mockEditor
+            .Setup(e => e.EditValue(mockContext.Object, mockProvider.Object, inputValue))
+            .Returns(expectedResult);
+
+        object result = _mockEditor.Object.EditValue(mockContext.Object, mockProvider.Object, inputValue);
+
+        result.Should().Be(expectedResult);
+    }
+
+    [Fact]
+    public void CreateInstance_CreatesListViewGroupWithUniqueName()
+    {
+        Mock<ListViewGroupCollection> mockCollection = new(new ListView());
+        _mockEditor.Object.TestAccessor().Dynamic._editValue = mockCollection.Object;
+
+        ListViewGroup? result = _mockEditor.Object.TestAccessor().Dynamic.CreateInstance(typeof(ListViewGroup)) as ListViewGroup;
+
+        result?.Name.Should().NotBeNull();
+        result?.Name.Should().StartWith("ListViewGroup");
+        result?.GetType().Should().Be(typeof(ListViewGroup));
+    }
+
+    [Fact]
+    public void CreateInstance_ThrowsException_WhenEditValueIsNull()
+    {
+        _mockEditor.Object.TestAccessor().Dynamic._editValue = null;
+
+        Action action = () => _mockEditor.Object.TestAccessor().Dynamic.CreateInstance(typeof(ListViewGroup));
+
+        action.Should().Throw<TargetInvocationException>();
+    }
+}