Test the shared Liberate icon renderings

Cover every icon in the finite set: each renders a valid PNG, no two render
alike, stoplights keep a common height, a PDF overlay only widens them, and
repeat requests are served from the cache.

Co-authored-by: rmcrackan <rmcrackan@gmail.com>

Source/_Tests/LibationUiBase.Tests/LibationUiBase.Tests.csproj

@@ -10,6 +10,9 @@
 
   <ItemGroup>
     <PackageReference Include="MSTest" Version="4.2.2" />
+    <!-- The Liberate icon tests rasterize with SkiaSharp, whose Linux native isn't
+         brought in by the SkiaSharp package itself the way Windows' and macOS' are. -->
+    <PackageReference Include="SkiaSharp.NativeAssets.Linux" Version="3.119.4" Condition="$([MSBuild]::IsOSPlatform('Linux'))" />
   </ItemGroup>
 
   <ItemGroup>

Source/_Tests/LibationUiBase.Tests/LiberateIconTests.cs

@@ -0,0 +1,116 @@
+using LibationUiBase.StatusIcons;
+
+namespace LibationUiBase.Tests;
+
+[TestClass]
+public class LiberateIconTests
+{
+	public static IEnumerable<object[]> AllIcons()
+		=> LiberateIconDescriptor.All().Select(d => new object[] { d });
+
+	[TestMethod]
+	[DynamicData(nameof(AllIcons))]
+	public void every_icon_renders_a_png(LiberateIconDescriptor descriptor)
+	{
+		var png = StatusImageGenerator.GetPng(descriptor);
+
+		var (width, height) = PngSize(png);
+		Assert.IsGreaterThan(0, width);
+		Assert.IsGreaterThan(0, height);
+	}
+
+	[TestMethod]
+	public void the_finite_set_of_icons_is_the_9_stoplights_plus_3_others_per_theme()
+	{
+		var all = LiberateIconDescriptor.All().ToList();
+
+		Assert.AreEqual(24, all.Count);
+		Assert.AreEqual(24, all.Distinct().Count());
+		Assert.AreEqual(18, all.Count(d => d.Kind is LiberateIconKind.Book));
+	}
+
+	[TestMethod]
+	public void every_icon_renders_differently()
+	{
+		var renderings = LiberateIconDescriptor.All()
+			.Select(d => Convert.ToHexString(StatusImageGenerator.GetPng(d)))
+			.ToList();
+
+		Assert.AreEqual(renderings.Count, renderings.Distinct().Count());
+	}
+
+	[TestMethod]
+	[DynamicData(nameof(AllIcons))]
+	public void renderings_are_cached(LiberateIconDescriptor descriptor)
+	{
+		//The grid asks for these constantly, and re-rendering is far more expensive than a lookup.
+		Assert.AreSame(StatusImageGenerator.GetPng(descriptor), StatusImageGenerator.GetPng(descriptor));
+	}
+
+	[TestMethod]
+	public void stoplights_are_all_the_same_height()
+	{
+		var heights = LiberateIconDescriptor.All()
+			.Where(d => d.Kind is LiberateIconKind.Book)
+			.Select(d => PngSize(StatusImageGenerator.GetPng(d)).Height)
+			.Distinct()
+			.ToList();
+
+		Assert.HasCount(1, heights);
+	}
+
+	[TestMethod]
+	[DataRow(PdfOverlay.Downloaded)]
+	[DataRow(PdfOverlay.NotDownloaded)]
+	public void a_pdf_overlay_widens_the_stoplight(PdfOverlay pdf)
+	{
+		var withoutPdf = PngSize(StatusImageGenerator.GetPng(LiberateIconDescriptor.ForBook(StoplightLamp.Green, PdfOverlay.None, isDark: false)));
+		var withPdf = PngSize(StatusImageGenerator.GetPng(LiberateIconDescriptor.ForBook(StoplightLamp.Green, pdf, isDark: false)));
+
+		Assert.IsGreaterThan(withoutPdf.Width, withPdf.Width);
+		Assert.AreEqual(withoutPdf.Height, withPdf.Height);
+	}
+
+	[TestMethod]
+	public void series_and_error_icons_do_not_vary_by_lamp_or_pdf()
+	{
+		//Otherwise every lamp/PDF combination would get its own cache entry for the same image.
+		Assert.AreEqual(LiberateIconDescriptor.ForSeries(expanded: true, isDark: false), LiberateIconDescriptor.ForSeries(expanded: true, isDark: false));
+		Assert.AreEqual(default, LiberateIconDescriptor.ForError(isDark: false).Lamp);
+		Assert.AreEqual(default, LiberateIconDescriptor.ForError(isDark: false).Pdf);
+		Assert.AreEqual(default, LiberateIconDescriptor.ForSeries(expanded: true, isDark: false).Lamp);
+		Assert.AreEqual(default, LiberateIconDescriptor.ForSeries(expanded: true, isDark: false).Pdf);
+	}
+
+	[TestMethod]
+	public void expanded_and_collapsed_series_icons_differ()
+	{
+		var collapsed = StatusImageGenerator.GetPng(LiberateIconDescriptor.ForSeries(expanded: false, isDark: false));
+		var expanded = StatusImageGenerator.GetPng(LiberateIconDescriptor.ForSeries(expanded: true, isDark: false));
+
+		Assert.AreNotEqual(Convert.ToHexString(collapsed), Convert.ToHexString(expanded));
+	}
+
+	[TestMethod]
+	public void icons_are_rendered_above_their_logical_size()
+	{
+		//WinForms sizes the icon from its pixel dimensions, so the scale has to divide evenly.
+		var (width, height) = PngSize(StatusImageGenerator.GetPng(LiberateIconDescriptor.ForError(isDark: false)));
+
+		Assert.IsGreaterThan(1, StatusImageGenerator.RenderScale);
+		Assert.AreEqual(0, width % StatusImageGenerator.RenderScale);
+		Assert.AreEqual(0, height % StatusImageGenerator.RenderScale);
+	}
+
+	/// <summary>Read the dimensions out of a PNG's IHDR, which also asserts that it is a PNG.</summary>
+	private static (int Width, int Height) PngSize(byte[] png)
+	{
+		Assert.IsNotNull(png);
+		Assert.IsGreaterThan(24, png.Length);
+		CollectionAssert.AreEqual(new byte[] { 0x89, (byte)'P', (byte)'N', (byte)'G', 0x0D, 0x0A, 0x1A, 0x0A }, png[..8]);
+
+		return (
+			System.Buffers.Binary.BinaryPrimitives.ReadInt32BigEndian(png.AsSpan(16, 4)),
+			System.Buffers.Binary.BinaryPrimitives.ReadInt32BigEndian(png.AsSpan(20, 4)));
+	}
+}