try to mitigate 32 bit failures

tests/ImageSharp.Tests/Formats/Gif/GifEncoderTests.cs

@@ -29,6 +29,15 @@ namespace SixLabors.ImageSharp.Tests.Formats.Gif
             { TestImages.Gif.Ratio4x1, 4, 1, PixelResolutionUnit.AspectRatio }
         };
 
+        public GifEncoderTests()
+        {
+            // Free the pool on 32 bit:
+            if (!TestEnvironment.Is64BitProcess)
+            {
+                Configuration.Default.MemoryAllocator.ReleaseRetainedResources();
+            }
+        }
+
         [Theory]
         [WithTestPatternImages(100, 100, TestPixelTypes, false)]
         [WithTestPatternImages(100, 100, TestPixelTypes, false)]

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

@@ -21,11 +21,17 @@ namespace SixLabors.ImageSharp.Tests
     public abstract partial class TestImageProvider<TPixel> : ITestImageProvider, IXunitSerializable
         where TPixel : unmanaged, IPixel<TPixel>
     {
+        public TestImageProvider()
+        {
+            this.Configuration = Configuration.CreateDefaultInstance();
+            this.Configuration.MemoryAllocator = Configuration.Default.MemoryAllocator;
+        }
+
         public PixelTypes PixelType { get; private set; } = typeof(TPixel).GetPixelType();
 
         public virtual string SourceFileOrDescription => string.Empty;
 
-        public Configuration Configuration { get; set; } = Configuration.CreateDefaultInstance();
+        public Configuration Configuration { get; set; }
 
         /// <summary>
         /// Gets the utility instance to provide information about the test image & manage input/output.