detecting mono runtime & skipping some png decoder tests

tests/ImageSharp.Tests/Formats/Png/PngDecoderTests.cs

@@ -11,6 +11,8 @@ using Xunit;
 
 namespace SixLabors.ImageSharp.Tests
 {
+    using System.Linq;
+
     using SixLabors.ImageSharp.Formats.Png;
     using SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison;
 
@@ -55,7 +57,8 @@ namespace SixLabors.ImageSharp.Tests
 
         public static readonly string[] CommonTestImages =
             {
-                TestImages.Png.Splash, TestImages.Png.Indexed,
+                TestImages.Png.Splash,
+                TestImages.Png.Indexed,
                 TestImages.Png.FilterVar,
                 TestImages.Png.Bad.ChunkLength1,
                 TestImages.Png.Bad.CorruptedChunk,
@@ -67,6 +70,9 @@ namespace SixLabors.ImageSharp.Tests
                 TestImages.Png.SnakeGame,
                 TestImages.Png.Banner7Adam7InterlaceMode,
                 TestImages.Png.Banner8Index,
+
+                TestImages.Png.Bad.ChunkLength2,
+                TestImages.Png.VimImage2,
             };
 
 
@@ -78,42 +84,42 @@ namespace SixLabors.ImageSharp.Tests
 
         // This is a workaround for Mono-s decoder being incompatible with ours and GDI+.
         // We shouldn't mix these with the Interleaved cases (which are also failing with Mono System.Drawing). Let's go AAA!
-        public static readonly string[] WindowsOnlyTestImages =
+        private static readonly string[] SkipOnMono =
             {
                 TestImages.Png.Bad.ChunkLength2,
                 TestImages.Png.VimImage2,
+                TestImages.Png.Splash,  
+                TestImages.Png.Indexed,
+                TestImages.Png.Bad.ChunkLength1,
+                TestImages.Png.VersioningImage1,
+                TestImages.Png.Banner7Adam7InterlaceMode,
             };
 
-        [Theory]
-        [WithFileCollection(nameof(CommonTestImages), PixelTypes.Rgba32)]
-        public void Decode<TPixel>(TestImageProvider<TPixel> provider)
-            where TPixel : struct, IPixel<TPixel>
+        private static bool SkipVerification(ITestImageProvider provider)
         {
-            using (Image<TPixel> image = provider.GetImage(new PngDecoder()))
-            {
-                image.DebugSave(provider);
-                image.CompareToOriginal(provider, ImageComparer.Exact);
-            }
+            string fn = provider.SourceFileOrDescription;
+
+            // This is a workaround for Mono-s decoder being incompatible with ours and GDI+.
+            // We shouldn't mix these with the Interleaved cases (which are also failing with Mono System.Drawing). Let's go AAA!
+            return (TestEnvironment.IsLinux || TestEnvironment.IsMono) && SkipOnMono.Contains(fn);
         }
 
-        // This is a workaround for Mono-s decoder being incompatible with ours and GDI+.
-        // We shouldn't mix these with the Interleaved cases (which are also failing with Mono System.Drawing). Let's go AAA!
         [Theory]
-        [WithFileCollection(nameof(WindowsOnlyTestImages), PixelTypes.Rgba32)]
-        public void Decode_WindowsOnlyTestImages<TPixel>(TestImageProvider<TPixel> provider)
+        [WithFileCollection(nameof(CommonTestImages), PixelTypes.Rgba32)]
+        public void Decode<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel>
         {
             using (Image<TPixel> image = provider.GetImage(new PngDecoder()))
             {
                 image.DebugSave(provider);
 
-                if (!TestEnvironment.IsLinux)
+                if (!SkipVerification(provider))
                 {
                     image.CompareToOriginal(provider, ImageComparer.Exact);
                 }
             }
         }
-
+        
         [Theory]
         [WithFile(TestImages.Png.Interlaced, PixelTypes.Rgba32)]
         public void Decode_Interlaced_DoesNotThrow<TPixel>(TestImageProvider<TPixel> provider)
@@ -148,7 +154,7 @@ namespace SixLabors.ImageSharp.Tests
                 image.DebugSave(provider);
 
                 // Workaround a bug in mono-s System.Drawing PNG decoder. It can't deal with 48Bpp png-s :(
-                if (!TestEnvironment.IsLinux)
+                if (!TestEnvironment.IsLinux && !TestEnvironment.IsMono)
                 {
                     image.CompareToOriginal(provider, ImageComparer.Exact);
                 }

tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs

@@ -124,6 +124,12 @@ namespace SixLabors.ImageSharp.Tests
                 // Does DebugSave & load reference CompareToReferenceInput():
                 string actualOutputFile = ((ITestImageProvider)provider).Utility.SaveTestOutputFile(image, "png", encoder, debugInfo, appendPixelType);
 
+                if (TestEnvironment.IsMono)
+                {
+                    // There are bugs in mono's System.Drawing implementation, reference decoders are not always reliable!
+                    return;
+                }
+
                 IImageDecoder referenceDecoder = TestEnvironment.GetReferenceDecoder(actualOutputFile);
                 string referenceOutputFile = ((ITestImageProvider)provider).Utility.GetReferenceOutputFileName("png", debugInfo, appendPixelType);
 

tests/ImageSharp.Tests/Memory/ArrayPoolMemoryManagerTests.cs

@@ -94,6 +94,12 @@ namespace SixLabors.ImageSharp.Tests.Memory
         [InlineData(MaxPooledBufferSizeInBytes + 1)]
         public void LargeBuffersAreNotPooled_OfByte(int size)
         {
+            if (!TestEnvironment.Is64BitProcess)
+            {
+                // can lead to OutOfMemoryException
+                return;
+            }
+
             Assert.False(this.CheckIsRentingPooledBuffer<byte>(size));
         }
 
@@ -108,6 +114,12 @@ namespace SixLabors.ImageSharp.Tests.Memory
         [Fact]
         public unsafe void LaregeBuffersAreNotPooled_OfBigValueType()
         {
+            if (!TestEnvironment.Is64BitProcess)
+            {
+                // can lead to OutOfMemoryException
+                return;
+            }
+
             int count = MaxPooledBufferSizeInBytes / sizeof(LargeStruct) + 1;
 
             Assert.False(this.CheckIsRentingPooledBuffer<LargeStruct>(count));
@@ -161,6 +173,12 @@ namespace SixLabors.ImageSharp.Tests.Memory
         [Fact]
         public void AllocationOverLargeArrayThreshold_UsesDifferentPool()
         {
+            if (!TestEnvironment.Is64BitProcess)
+            {
+                // can lead to OutOfMemoryException
+                return;
+            }
+
             int arrayLengthThreshold = PoolSelectorThresholdInBytes / sizeof(int);
 
             IBuffer<int> small = this.MemoryManager.Allocate<int>(arrayLengthThreshold - 1);

tests/ImageSharp.Tests/TestUtilities/ImageProviders/TestImageProvider.cs

@@ -19,7 +19,9 @@ namespace SixLabors.ImageSharp.Tests
     {
         PixelTypes PixelType { get; }
         ImagingTestCaseUtility Utility { get; }
+        string SourceFileOrDescription { get; }
     }
+
     /// <summary>
     /// Provides <see cref="Image{TPixel}" /> instances for parametric unit tests.
     /// </summary>

tests/ImageSharp.Tests/TestUtilities/TestEnvironment.cs

@@ -92,6 +92,8 @@ namespace SixLabors.ImageSharp.Tests
             actualOutputFileName.Replace("ActualOutput", @"External\ReferenceOutput").Replace('\\', Path.DirectorySeparatorChar);
 
         internal static bool IsLinux => RuntimeInformation.IsOSPlatform(OSPlatform.Linux);
+        
+        internal static bool IsMono => Type.GetType("Mono.Runtime") != null; // https://stackoverflow.com/a/721194
 
         internal static bool IsWindows => RuntimeInformation.IsOSPlatform(OSPlatform.Windows);