diff --git a/tests/ImageSharp.Tests/Formats/Gif/GifEncoderTests.cs b/tests/ImageSharp.Tests/Formats/Gif/GifEncoderTests.cs
index a06e36e2a..a2f4806f3 100644
--- a/tests/ImageSharp.Tests/Formats/Gif/GifEncoderTests.cs
+++ b/tests/ImageSharp.Tests/Formats/Gif/GifEncoderTests.cs
@@ -7,15 +7,16 @@ using SixLabors.ImageSharp.Formats.Gif;
 using SixLabors.ImageSharp.MetaData;
 using SixLabors.ImageSharp.PixelFormats;
 using Xunit;
+// ReSharper disable InconsistentNaming
 
 namespace SixLabors.ImageSharp.Tests
 {
     public class GifEncoderTests
     {
-        private const PixelTypes PixelTypes = Tests.PixelTypes.Rgba32 | Tests.PixelTypes.RgbaVector | Tests.PixelTypes.Argb32;
+        private const PixelTypes TestPixelTypes = PixelTypes.Rgba32 | PixelTypes.RgbaVector | PixelTypes.Argb32;
 
         [Theory]
-        [WithTestPatternImages(100, 100, PixelTypes)]
+        [WithTestPatternImages(100, 100, TestPixelTypes)]
         public void EncodeGeneratedPatterns<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel>
         {
@@ -78,7 +79,7 @@ namespace SixLabors.ImageSharp.Tests
         }
 
         [Fact]
-        public void Encode_CommentIsToLong_CommentIsTrimmed()
+        public void Encode_WhenCommentIsTooLong_CommentIsTrimmed()
         {
             using (Image<Rgba32> input = new Image<Rgba32>(1, 1))
             {
diff --git a/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs b/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs
index 1566ddf44..ef261aac9 100644
--- a/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs
+++ b/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs
@@ -10,36 +10,127 @@ using SixLabors.ImageSharp.Formats.Png;
 using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.PixelFormats;
 using Xunit;
+// ReSharper disable InconsistentNaming
 
 namespace SixLabors.ImageSharp.Tests
 {
+    using SixLabors.ImageSharp.Quantizers;
+    using SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison;
+
     public class PngEncoderTests : FileTestBase
     {
-        private const PixelTypes PixelTypes = Tests.PixelTypes.Rgba32 | Tests.PixelTypes.RgbaVector | Tests.PixelTypes.Argb32;
+        /// <summary>
+        /// All types except Palette
+        /// </summary>
+        public static readonly TheoryData<PngColorType> PngColorTypes = new TheoryData<PngColorType>()
+                                                                           {
+                                                                               PngColorType.RgbWithAlpha,
+                                                                               PngColorType.Rgb,
+                                                                               PngColorType.Grayscale,
+                                                                               PngColorType.GrayscaleWithAlpha,
+                                                                           };
+
+        /// <summary>
+        /// All types except Palette
+        /// </summary>
+        public static readonly TheoryData<int> CompressionLevels = new TheoryData<int>()
+                                                                            {
+                                                                                1, 2, 3, 4, 5, 6, 7, 8, 9
+                                                                            };
+
+        public static readonly TheoryData<int> PaletteSizes = new TheoryData<int>()
+                                                                  {
+                                                                      30, 55, 100, 201, 255
+                                                                  };
+
+        [Theory]
+        [WithTestPatternImages(nameof(PngColorTypes), 48, 24, PixelTypes.Rgba32)]
+        [WithTestPatternImages(nameof(PngColorTypes), 47, 8, PixelTypes.Rgba32)]
+        [WithTestPatternImages(nameof(PngColorTypes), 49, 7, PixelTypes.Rgba32)]
+        [WithSolidFilledImages(nameof(PngColorTypes), 1, 1, 255, 100, 50, 255, PixelTypes.Rgba32)]
+        [WithTestPatternImages(nameof(PngColorTypes), 7, 5, PixelTypes.Rgba32)]
+        public void WorksWithDifferentSizes<TPixel>(TestImageProvider<TPixel> provider, PngColorType pngColorType)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            TestPngEncoderCore(provider, pngColorType, appendPngColorType: true);
+        }
+
+        [Theory]
+        [WithTestPatternImages(nameof(PngColorTypes), 24, 24, PixelTypes.Rgba32 | PixelTypes.Bgra32 | PixelTypes.Rgb24)]
+        public void IsNotBoundToSinglePixelType<TPixel>(TestImageProvider<TPixel> provider, PngColorType pngColorType)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            TestPngEncoderCore(provider, pngColorType, appendPixelType: true);
+        }
+
+        [Theory]
+        [WithTestPatternImages(nameof(CompressionLevels), 24, 24, PixelTypes.Rgba32)]
+        public void WorksWithAllCompressionLevels<TPixel>(TestImageProvider<TPixel> provider, int compressionLevel)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            TestPngEncoderCore(provider, PngColorType.RgbWithAlpha, compressionLevel, appendCompressionLevel: true);
+        }
 
         [Theory]
-        [WithTestPatternImages(100, 100, PixelTypes, PngColorType.RgbWithAlpha)]
-        [WithTestPatternImages(100, 100, PixelTypes, PngColorType.Rgb)]
-        [WithTestPatternImages(100, 100, PixelTypes, PngColorType.Palette)]
-        [WithTestPatternImages(100, 100, PixelTypes, PngColorType.Grayscale)]
-        [WithTestPatternImages(100, 100, PixelTypes, PngColorType.GrayscaleWithAlpha)]
-        public void EncodeGeneratedPatterns<TPixel>(TestImageProvider<TPixel> provider, PngColorType pngColorType)
+        [WithTestPatternImages(nameof(PaletteSizes), 72, 72, PixelTypes.Rgba32)]
+        public void PaletteColorType_WuQuantizer<TPixel>(TestImageProvider<TPixel> provider, int paletteSize)
             where TPixel : struct, IPixel<TPixel>
         {
             using (Image<TPixel> image = provider.GetImage())
             {
-                var options = new PngEncoder()
-                {
-                    PngColorType = pngColorType
-                };
-                provider.Utility.TestName += "_" + pngColorType;
+                var encoder = new PngEncoder
+                                  {
+                                      PngColorType = PngColorType.Palette,
+                                      PaletteSize = paletteSize,
+                                      Quantizer = new WuQuantizer<TPixel>()
+                                  };
 
-                provider.Utility.SaveTestOutputFile(image, "png", options);
+                image.VerifyEncoder(provider, "png", $"PaletteSize-{paletteSize}", encoder, appendPixelTypeToFileName: false);
             }
         }
 
+        private static bool HasAlpha(PngColorType pngColorType) =>
+            pngColorType == PngColorType.GrayscaleWithAlpha || pngColorType == PngColorType.RgbWithAlpha;
+
+        private static void TestPngEncoderCore<TPixel>(
+            TestImageProvider<TPixel> provider,
+            PngColorType pngColorType,
+            int compressionLevel = 6,
+            bool appendPngColorType = false,
+            bool appendPixelType = false,
+            bool appendCompressionLevel = false)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            using (Image<TPixel> image = provider.GetImage())
+            {
+                if (!HasAlpha(pngColorType))
+                {
+                    image.Mutate(c => c.Opacity(1));
+                }
+
+                var encoder = new PngEncoder { PngColorType = pngColorType, CompressionLevel = compressionLevel};
+
+                string pngColorTypeInfo = appendPixelType ? pngColorType.ToString() : "";
+                string compressionLevelInfo = appendCompressionLevel ? $"_C{compressionLevel}" : "";
+                string debugInfo = $"{pngColorTypeInfo}{compressionLevelInfo}";
+                string referenceInfo = $"{pngColorTypeInfo}";
+
+                // Does DebugSave & load reference CompareToReferenceInput():
+                string path = ((ITestImageProvider)provider).Utility.SaveTestOutputFile(image, "png", encoder, debugInfo, appendPixelType);
+            
+                IImageDecoder referenceDecoder = TestEnvironment.GetReferenceDecoder(path);
+                string referenceOutputFile = ((ITestImageProvider)provider).Utility.GetReferenceOutputFileName("png", referenceInfo, appendPixelType);
+            
+                using (var encodedImage = Image.Load<TPixel>(referenceOutputFile, referenceDecoder))
+                {
+                    ImageComparer comparer = null ?? ImageComparer.Exact;
+                    comparer.CompareImagesOrFrames(image, encodedImage);
+                }
+            }
+        }
+        
         [Theory]
-        [WithBlankImages(1, 1, PixelTypes.All)]
+        [WithBlankImages(1, 1, PixelTypes.Rgba32)]
         public void WritesFileMarker<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel>
         {
diff --git a/tests/Images/External b/tests/Images/External
index 65db1d045..06809c1f2 160000
--- a/tests/Images/External
+++ b/tests/Images/External
@@ -1 +1 @@
-Subproject commit 65db1d045e74e7702ec33b44f88f97b4bf86f1ea
+Subproject commit 06809c1f2462332731f2a88bd866d5222f533aa5