skip some of the MemoryManager tests on 32 bit

tests/ImageSharp.Tests/Memory/ArrayPoolMemoryManagerTests.cs

@@ -175,6 +175,12 @@ namespace SixLabors.ImageSharp.Tests.Memory
         [Fact]
         public void CreateWithAggressivePooling()
         {
+            if (!TestEnvironment.Is64BitProcess)
+            {
+                // can lead to OutOfMemoryException
+                return;
+            }
+
             this.MemoryManager = ArrayPoolMemoryManager.CreateWithAggressivePooling();
 
             Assert.True(this.CheckIsRentingPooledBuffer<Rgba32>(4096 * 4096));
@@ -183,6 +189,12 @@ namespace SixLabors.ImageSharp.Tests.Memory
         [Fact]
         public void CreateDefault()
         {
+            if (!TestEnvironment.Is64BitProcess)
+            {
+                // can lead to OutOfMemoryException
+                return;
+            }
+
             this.MemoryManager = ArrayPoolMemoryManager.CreateDefault();
 
             Assert.False(this.CheckIsRentingPooledBuffer<Rgba32>(2 * 4096 * 4096));
@@ -192,6 +204,12 @@ namespace SixLabors.ImageSharp.Tests.Memory
         [Fact]
         public void CreateWithModeratePooling()
         {
+            if (!TestEnvironment.Is64BitProcess)
+            {
+                // can lead to OutOfMemoryException
+                return;
+            }
+
             this.MemoryManager = ArrayPoolMemoryManager.CreateWithModeratePooling();
 
             Assert.False(this.CheckIsRentingPooledBuffer<Rgba32>(2048 * 2048));

tests/ImageSharp.Tests/TestUtilities/TestUtils.cs

@@ -169,6 +169,7 @@ namespace SixLabors.ImageSharp.Tests
             {
                 comparer = ImageComparer.Tolerant(0.5f / 100);
             }
+
             using (Image<TPixel> image = provider.GetImage())
             {
                 image.Mutate(process);
@@ -192,12 +193,17 @@ namespace SixLabors.ImageSharp.Tests
             ImageComparer comparer = null)
             where TPixel : struct, IPixel<TPixel>
         {
+            if (comparer == null)
+            {
+                comparer = ImageComparer.Tolerant(0.5f / 100);
+            }
+
             using (Image<TPixel> image = provider.GetImage())
             {
                 var bounds = new Rectangle(image.Width / 4, image.Width / 4, image.Width / 2, image.Height / 2);
                 image.Mutate(x => process(x, bounds));
                 image.DebugSave(provider, testOutputDetails);
-                image.CompareToReferenceOutput(provider, testOutputDetails);
+                image.CompareToReferenceOutput(comparer, provider, testOutputDetails);
             }
         }