Update PixelSamplingStrategyTests.cs

tests/ImageSharp.Tests/Quantization/PixelSamplingStrategyTests.cs

@@ -10,24 +10,36 @@ namespace SixLabors.ImageSharp.Tests.Quantization;
 
 public class PixelSamplingStrategyTests
 {
-    public static readonly TheoryData<int, int, int, int> DefaultPixelSamplingStrategy_Data = new TheoryData<int, int, int, int>()
-        {
-            { 100, 100, 1, 10000 },
-            { 100, 100, 1, 5000 },
-            { 100, 100, 10, 50000 },
-            { 99, 100, 11, 30000 },
-            { 97, 99, 11, 80000 },
-            { 99, 100, 11, 20000 },
-            { 99, 501, 20, 100000 },
-            { 97, 500, 20, 10000 },
-            { 103, 501, 20, 1000 },
-        };
+    public static readonly TheoryData<int, int, int, int> DefaultPixelSamplingStrategy_MultiFrame_Data = new()
+    {
+        { 100, 100, 1, 10000 },
+        { 100, 100, 1, 5000 },
+        { 100, 100, 10, 50000 },
+        { 99, 100, 11, 30000 },
+        { 97, 99, 11, 80000 },
+        { 99, 100, 11, 20000 },
+        { 99, 501, 20, 100000 },
+        { 97, 500, 20, 10000 },
+        { 103, 501, 20, 1000 },
+    };
+
+    public static readonly TheoryData<int, int, int> DefaultPixelSamplingStrategy_Data = new()
+    {
+        { 100, 100, 9900 },
+        { 100, 100, 5000 },
+        { 99, 100, 30000 },
+        { 97, 99, 80000 },
+        { 99, 100, 20000 },
+        { 99, 501, 100000 },
+        { 97, 500, 10000 },
+        { 103, 501, 1000 },
+    };
 
     [Fact]
     public void ExtensivePixelSamplingStrategy_EnumeratesAll()
     {
         using Image<L8> image = CreateTestImage(100, 100, 100);
-        var strategy = new ExtensivePixelSamplingStrategy();
+        ExtensivePixelSamplingStrategy strategy = new();
 
         foreach (Buffer2DRegion<L8> region in strategy.EnumeratePixelRegions(image))
         {
@@ -40,12 +52,12 @@ public class PixelSamplingStrategyTests
     }
 
     [Theory]
-    [WithBlankImages(nameof(DefaultPixelSamplingStrategy_Data), 1, 1, PixelTypes.L8)]
-    public void DefaultPixelSamplingStrategy_IsFair(TestImageProvider<L8> dummyProvider, int width, int height, int noOfFrames, int maximumNumberOfPixels)
+    [WithBlankImages(nameof(DefaultPixelSamplingStrategy_MultiFrame_Data), 1, 1, PixelTypes.L8)]
+    public void DefaultPixelSamplingStrategy_IsFair_MultiFrame(TestImageProvider<L8> dummyProvider, int width, int height, int noOfFrames, int maximumNumberOfPixels)
     {
         using Image<L8> image = CreateTestImage(width, height, noOfFrames);
 
-        var strategy = new DefaultPixelSamplingStrategy(maximumNumberOfPixels, 0.1);
+        DefaultPixelSamplingStrategy strategy = new(maximumNumberOfPixels, 0.1);
 
         long visitedPixels = 0;
         foreach (Buffer2DRegion<L8> region in strategy.EnumeratePixelRegions(image))
@@ -67,9 +79,37 @@ public class PixelSamplingStrategyTests
         Assert.True(visitRatio <= 1.1, $"{visitedPixels}>{maximumPixels}");
     }
 
+    [Theory]
+    [WithBlankImages(nameof(DefaultPixelSamplingStrategy_Data), 1, 1, PixelTypes.L8)]
+    public void DefaultPixelSamplingStrategy_IsFair(TestImageProvider<L8> dummyProvider, int width, int height, int maximumNumberOfPixels)
+    {
+        using Image<L8> image = CreateTestImage(width, height, 1);
+
+        DefaultPixelSamplingStrategy strategy = new(maximumNumberOfPixels, 0.1);
+
+        long visitedPixels = 0;
+        foreach (Buffer2DRegion<L8> region in strategy.EnumeratePixelRegions(image))
+        {
+            PaintWhite(region);
+            visitedPixels += region.Width * region.Height;
+        }
+
+        image.DebugSave(
+            dummyProvider,
+            $"W{width}_H{height}_maximumNumberOfPixels_{maximumNumberOfPixels}",
+            appendPixelTypeToFileName: false);
+
+        int maximumPixels = image.Width * image.Height * image.Frames.Count / 10;
+        maximumPixels = Math.Max(maximumPixels, (int)strategy.MaximumPixels);
+
+        // allow some inaccuracy:
+        double visitRatio = visitedPixels / (double)maximumPixels;
+        Assert.True(visitRatio <= 1.1, $"{visitedPixels}>{maximumPixels}");
+    }
+
     private static void PaintWhite(Buffer2DRegion<L8> region)
     {
-        var white = new L8(255);
+        L8 white = new(255);
         for (int y = 0; y < region.Height; y++)
         {
             region.DangerousGetRowSpan(y).Fill(white);
@@ -79,7 +119,7 @@ public class PixelSamplingStrategyTests
     private static Image<L8> CreateTestImage(int width, int height, int noOfFrames, bool paintWhite = false)
     {
         L8 bg = paintWhite ? new L8(255) : default;
-        var image = new Image<L8>(width, height, bg);
+        Image<L8> image = new(width, height, bg);
 
         for (int i = 1; i < noOfFrames; i++)
         {