Add code coverage for RadioButtonPopupAdapter

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

@@ -0,0 +1,92 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Drawing;
+using System.Windows.Forms.ButtonInternal;
+
+namespace System.Windows.Forms.Tests;
+
+public class RadioButtonPopupAdapterTests
+{
+    private class TestRadioButton : RadioButton
+    {
+        public TestRadioButton()
+        {
+        }
+    }
+
+    private class TestRadioButtonPopupAdapter : RadioButtonPopupAdapter
+    {
+        public TestRadioButtonPopupAdapter(ButtonBase control) : base(control)
+        {
+        }
+
+        public void CallPaintUp(PaintEventArgs e, CheckState state) => PaintUp(e, state);
+        public void CallPaintOver(PaintEventArgs e, CheckState state) => PaintOver(e, state);
+        public void CallPaintDown(PaintEventArgs e, CheckState state) => PaintDown(e, state);
+        public LayoutOptions CallLayout(PaintEventArgs e) => Layout(e);
+        public ButtonBaseAdapter CallCreateButtonAdapter() => CreateButtonAdapter();
+    }
+
+    private static (TestRadioButton, TestRadioButtonPopupAdapter) CreateAdapter()
+    {
+        TestRadioButton radioButton = new();
+        TestRadioButtonPopupAdapter adapter = new(radioButton);
+
+        return (radioButton, adapter);
+    }
+
+    [WinFormsFact]
+    public void PaintUp_ButtonAppearance_DelegatesToButtonPopupAdapter()
+    {
+        (TestRadioButton radioButton, TestRadioButtonPopupAdapter adapter) = CreateAdapter();
+        radioButton.Appearance = Appearance.Button;
+        using Bitmap bmp = new(20, 20);
+        using Graphics g = Graphics.FromImage(bmp);
+        using PaintEventArgs e = new(g, new Rectangle(0, 0, 20, 20));
+
+        adapter.CallPaintUp(e, CheckState.Checked);
+
+        bool anyPixelChanged = false;
+        Color defaultColor = bmp.GetPixel(0, 0);
+        for (int x = 0; x < bmp.Width && !anyPixelChanged; x++)
+        {
+            for (int y = 0; y < bmp.Height && !anyPixelChanged; y++)
+            {
+                if (bmp.GetPixel(x, y) != defaultColor)
+                {
+                    anyPixelChanged = true;
+                }
+            }
+        }
+
+        anyPixelChanged.Should().BeTrue("PaintUp should modify the bitmap when Appearance is Button.");
+    }
+
+    [WinFormsFact]
+    public void PaintUp_RadioAppearance_Draws()
+    {
+        (TestRadioButton radioButton, TestRadioButtonPopupAdapter adapter) = CreateAdapter();
+        radioButton.Appearance = Appearance.Normal;
+        using Bitmap bmp = new(20, 20);
+        using Graphics g = Graphics.FromImage(bmp);
+        using PaintEventArgs e = new(g, new Rectangle(0, 0, 20, 20));
+
+        adapter.CallPaintUp(e, CheckState.Checked);
+
+        bool anyPixelChanged = false;
+        Color defaultColor = bmp.GetPixel(0, 0);
+        for (int x = 0; x < bmp.Width && !anyPixelChanged; x++)
+        {
+            for (int y = 0; y < bmp.Height && !anyPixelChanged; y++)
+            {
+                if (bmp.GetPixel(x, y) != defaultColor)
+                {
+                    anyPixelChanged = true;
+                }
+            }
+        }
+
+        anyPixelChanged.Should().BeTrue("PaintUp should modify the bitmap when Appearance is Normal.");
+    }
+}