fix tests

tests/ImageSharp.Tests/Memory/Allocators/UniformUnmanagedMemoryPoolTests.Trim.cs

@@ -36,7 +36,7 @@ namespace SixLabors.ImageSharp.Tests.Memory.Allocators
                     UnmanagedMemoryHandle[] b = pool.Rent(64);
                     pool.Return(a);
                     Assert.Equal(128, UnmanagedMemoryHandle.TotalOutstandingHandles);
-                    Thread.Sleep(20_000);
+                    Thread.Sleep(15_000);
 
                     // We expect at least 2 Trim actions, first trim 32, then 16 arrays.
                     // 128 - 32 - 16 = 80
@@ -70,10 +70,12 @@ namespace SixLabors.ImageSharp.Tests.Memory.Allocators
                     GC.WaitForPendingFinalizers();
                     Assert.Equal(128, UnmanagedMemoryHandle.TotalOutstandingHandles);
 
-                    Thread.Sleep(20_000);
+                    Thread.Sleep(15_000);
                     Assert.True(
                         UnmanagedMemoryHandle.TotalOutstandingHandles <= 64,
                         $"UnmanagedMemoryHandle.TotalOutstandingHandles={UnmanagedMemoryHandle.TotalOutstandingHandles} > 64");
+                    GC.KeepAlive(pool1);
+                    GC.KeepAlive(pool2);
                 }
 
                 [MethodImpl(MethodImplOptions.NoInlining)]

tests/ImageSharp.Tests/Memory/Allocators/UniformUnmanagedPoolMemoryAllocatorTests.cs

@@ -253,6 +253,7 @@ namespace SixLabors.ImageSharp.Tests.Memory.Allocators
             }
         }
 
+        [Theory]
         [InlineData(300)]
         [InlineData(600)]
         [InlineData(1200)]
@@ -302,6 +303,7 @@ namespace SixLabors.ImageSharp.Tests.Memory.Allocators
             }
         }
 
+        [Theory]
         [InlineData(300)]
         [InlineData(600)]
         public void MemoryOwnerFinalizer_ReturnsToPool(int length)