Add unit test for ImageListImage (#11736)

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

@@ -0,0 +1,89 @@
+// 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.Drawing;
+
+namespace System.Windows.Forms.Design.Tests;
+
+public sealed class ImageListImageTests
+{
+    [Fact]
+    public void Constructor_WithImage_ShouldSetImageProperty()
+    {
+        using Bitmap bitmap = new(10, 10);
+        ImageListImage imageListImage = new(bitmap);
+
+        imageListImage.Image.Should().Be(bitmap);
+        imageListImage.Name.Should().BeEmpty();
+    }
+
+    [Fact]
+    public void Constructor_WithImageAndName_ShouldSetImageAndNameProperties()
+    {
+        using Bitmap bitmap = new(10, 10);
+        string name = "TestImage";
+        ImageListImage imageListImage = new(bitmap, name);
+
+        imageListImage.Image.Should().Be(bitmap);
+        imageListImage.Name.Should().Be(name);
+    }
+
+    [Fact]
+    public void NameProperty_ShouldGetAndSetCorrectly()
+    {
+        using Bitmap bitmap = new(10, 10);
+        string name = "TestImage";
+        ImageListImage imageListImage = new(bitmap)
+        {
+            Name = name
+        };
+
+        imageListImage.Name.Should().Be(name);
+    }
+
+    [Fact]
+    public void NameProperty_ShouldReturnEmptyString_WhenNameIsNull()
+    {
+        using Bitmap bitmap = new(10, 10);
+        ImageListImage imageListImage = new(bitmap)
+        {
+            Name = null
+        };
+
+        imageListImage.Name.Should().BeEmpty();
+    }
+
+    [Fact]
+    public void ImageListImageFromStream_ShouldCreateImageListImageFromBitmapStream()
+    {
+        using Bitmap bitmap = new(10, 10);
+        using MemoryStream memoryStream = new();
+        bitmap.Save(memoryStream, Drawing.Imaging.ImageFormat.Bmp);
+        memoryStream.Seek(0, SeekOrigin.Begin);
+
+        var result = ImageListImage.ImageListImageFromStream(memoryStream, imageIsIcon: false);
+
+        result.Should().NotBeNull();
+        result.Image.Should().NotBeNull();
+        result.Image.Size.Should().Be(bitmap.Size);
+        result.Image.RawFormat.Should().Be(expected: Drawing.Imaging.ImageFormat.Bmp);
+    }
+
+    [Fact]
+    public void ImageListImageFromStream_ShouldCreateImageListImageFromIconStream()
+    {
+        using Icon icon = SystemIcons.Application;
+        using MemoryStream memoryStream = new();
+        icon.Save(memoryStream);
+        memoryStream.Seek(0, SeekOrigin.Begin);
+
+        var result = ImageListImage.ImageListImageFromStream(memoryStream, imageIsIcon: true);
+
+        result.Should().NotBeNull();
+        result.Image.Should().NotBeNull();
+        result.Image.Size.Should().Be(icon.Size);
+        result.Image.RawFormat.Should().Be(Drawing.Imaging.ImageFormat.MemoryBmp);
+    }
+}