Add code coverage for FlowLayoutPanelDesigner.cs file (#13257)

* Add code coverage for FlowLayoutPanelDesigner.cs file
Related #10773

Author: Olina-Zhang

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

@@ -0,0 +1,208 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections;
+using System.ComponentModel;
+using System.ComponentModel.Design;
+using System.Drawing;
+using Moq;
+
+namespace System.Windows.Forms.Design.Tests;
+
+public class FlowLayoutPanelDesignerTests : IDisposable
+{
+    private readonly Mock<IServiceProvider> _serviceProviderMock;
+    private readonly Mock<IDesignerHost> _designerHostMock;
+    private readonly Mock<ISelectionService> _selectionServiceMock;
+    private readonly FlowLayoutPanelDesigner _designer;
+    private readonly FlowLayoutPanel _flowLayoutPanel;
+
+    public FlowLayoutPanelDesignerTests()
+    {
+        _serviceProviderMock = new();
+        _designerHostMock = new();
+        _selectionServiceMock = new();
+
+        _serviceProviderMock.Setup(s => s.GetService(typeof(IDesignerHost))).Returns(_designerHostMock.Object);
+        _serviceProviderMock.Setup(s => s.GetService(typeof(ISelectionService))).Returns(_selectionServiceMock.Object);
+
+        _flowLayoutPanel = new() { Site = new Mock<ISite>().Object };
+        _designer = new();
+        _designer.Initialize(_flowLayoutPanel);
+    }
+
+    public void Dispose()
+    {
+        _designer.Dispose();
+        _flowLayoutPanel.Dispose();
+    }
+
+    [Fact]
+    public void Initialize_ShouldSetInheritedReadOnlyAttribute_WhenFlowLayoutPanelIsInheritedReadOnly()
+    {
+        using Control childControl = new() { Site = new Mock<ISite>().Object };
+        _flowLayoutPanel.Controls.Add(childControl);
+
+        TypeDescriptor.AddAttributes(childControl, InheritanceAttribute.InheritedReadOnly);
+
+        TypeDescriptor.GetAttributes(childControl)[typeof(InheritanceAttribute)]
+            .Should().BeEquivalentTo(InheritanceAttribute.InheritedReadOnly);
+    }
+
+    [Fact]
+    public void Initialize_ShouldBeNotInheritedAttribute_WhenFlowLayoutPanelIsNotInheritedReadOnly()
+    {
+        using Control childControl = new() { Site = new Mock<ISite>().Object };
+        _flowLayoutPanel.Controls.Add(childControl);
+
+        TypeDescriptor.GetAttributes(childControl)[typeof(InheritanceAttribute)]
+            .Should().NotBeEquivalentTo(InheritanceAttribute.InheritedReadOnly);
+    }
+
+    [Fact]
+    public void PreFilterProperties_ShouldModifyFlowDirectionProperty()
+    {
+        Hashtable properties = new()
+        {
+            { nameof(FlowLayoutPanel.FlowDirection), TypeDescriptor.CreateProperty(typeof(FlowLayoutPanel), nameof(FlowLayoutPanel.FlowDirection), typeof(FlowDirection)) }
+        };
+
+        _designer.TestAccessor().Dynamic.PreFilterProperties(properties);
+
+        properties[nameof(FlowLayoutPanel.FlowDirection)].Should().NotBeNull();
+        properties[nameof(FlowLayoutPanel.FlowDirection)].Should().BeAssignableTo<PropertyDescriptor>();
+    }
+
+    [Fact]
+    public void AllowSetChildIndexOnDrop_ShouldReturnFalse() =>
+        _designer.AllowSetChildIndexOnDrop.Should().BeFalse();
+
+    [Fact]
+    public void AllowGenericDragBox_ShouldReturnFalse()
+    {
+        bool result = _designer.TestAccessor().Dynamic.AllowGenericDragBox;
+
+        result.Should().BeFalse();
+    }
+
+    [Theory]
+    [InlineData(FlowDirection.LeftToRight, true)]
+    [InlineData(FlowDirection.RightToLeft, true)]
+    [InlineData(FlowDirection.TopDown, false)]
+    [InlineData(FlowDirection.BottomUp, false)]
+    public void HorizontalFlow_ShouldReturnCorrectValueBasedOnFlowDirection(FlowDirection flowDirection, bool expected)
+    {
+        _flowLayoutPanel.FlowDirection = flowDirection;
+
+        bool result = _designer.TestAccessor().Dynamic.HorizontalFlow;
+
+        result.Should().Be(expected);
+    }
+
+    [Theory]
+    [InlineData(FlowDirection.LeftToRight, FlowDirection.RightToLeft)]
+    [InlineData(FlowDirection.RightToLeft, FlowDirection.LeftToRight)]
+    [InlineData(FlowDirection.TopDown, FlowDirection.TopDown)]
+    [InlineData(FlowDirection.BottomUp, FlowDirection.BottomUp)]
+    public void RTLTranslateFlowDirection_ShouldTranslateCorrectly(FlowDirection input, FlowDirection expected)
+    {
+        _flowLayoutPanel.RightToLeft = RightToLeft.Yes;
+
+        FlowDirection result = _designer.TestAccessor().Dynamic.RTLTranslateFlowDirection(input);
+
+        result.Should().Be(expected);
+    }
+
+    [Theory]
+    [InlineData(RightToLeft.Yes, true)]
+    [InlineData(RightToLeft.No, false)]
+    public void IsRtl_ShouldReturnCorrectValueBasedOnRightToLeft(RightToLeft rightToLeft, bool expected)
+    {
+        _flowLayoutPanel.RightToLeft = rightToLeft;
+
+        bool result = _designer.TestAccessor().Dynamic.IsRtl;
+
+        result.Should().Be(expected);
+    }
+
+    [Fact]
+    public void GetMarginBounds_ShouldReturnCorrectRectangle()
+    {
+        using Control control = new()
+        {
+            Bounds = new Rectangle(10, 20, 30, 40),
+            Margin = new Padding(5, 6, 7, 8)
+        };
+
+        Rectangle result = _designer.TestAccessor().Dynamic.GetMarginBounds(control);
+
+        result.Should().Be(new Rectangle(5, 14, 42, 54));
+    }
+
+    [Fact]
+    public void OnDragEnter_ShouldInitializeDragState()
+    {
+        DragEventArgs dragEventArgs = new(
+            new DataObject(),
+            0,
+            0,
+            0,
+            DragDropEffects.Copy,
+            DragDropEffects.Copy);
+
+        _designer.TestAccessor().Dynamic.OnDragEnter(dragEventArgs);
+
+        int insertionIndex = _designer.TestAccessor().Dynamic._insertionIndex;
+        insertionIndex.Should().Be(-1);
+
+        Point lastMouseLocation = _designer.TestAccessor().Dynamic._lastMouseLocation;
+        lastMouseLocation.Should().Be(Point.Empty);
+    }
+
+    [Fact]
+    public void OnDragLeave_ShouldClearDragState()
+    {
+        _designer.TestAccessor().Dynamic.OnDragLeave(EventArgs.Empty);
+
+        int insertionIndex = _designer.TestAccessor().Dynamic._insertionIndex;
+        insertionIndex.Should().Be(-1);
+    }
+
+    [Fact]
+    public void OnDragOver_ShouldUpdateInsertionIndex()
+    {
+        DragEventArgs dragEventArgs = new(
+            new DataObject(),
+            0,
+            10,
+            10,
+            DragDropEffects.Copy,
+            DragDropEffects.Copy);
+
+        _designer.TestAccessor().Dynamic.OnDragOver(dragEventArgs);
+
+        int insertionIndex = _designer.TestAccessor().Dynamic._insertionIndex;
+        insertionIndex.Should().Be(-1);
+    }
+
+    [Fact]
+    public void OnDragDrop_ShouldReorderControls()
+    {
+        using Control control1 = new();
+        using Control control2 = new();
+        _flowLayoutPanel.Controls.Add(control1);
+        _flowLayoutPanel.Controls.Add(control2);
+        DragEventArgs dragEventArgs = new(
+            new DataObject(),
+            0,
+            0,
+            0,
+            DragDropEffects.Move,
+            DragDropEffects.Move);
+
+        _designer.TestAccessor().Dynamic.OnDragDrop(dragEventArgs);
+
+        _flowLayoutPanel.Controls[0].Should().Be(control1);
+        _flowLayoutPanel.Controls[1].Should().Be(control2);
+    }
+}