Fix flaky cache statistics test

Agent-Logs-Url: https://github.com/securefolderfs-community/SecureFolderFS/sessions/a546110b-189b-4498-8f4a-511e0a60aea2

Co-authored-by: d2dyno1 <53011783+d2dyno1@users.noreply.github.com>

Author: Copilot

tests/SecureFolderFS.Tests/FileSystemTests/FileSystemCacheTests.cs

@@ -1,4 +1,6 @@
+using System;
 using System.Text;
+using System.Threading;
 using FluentAssertions;
 using NUnit.Framework;
 using OwlCore.Storage;
@@ -38,12 +40,12 @@ public async Task Write_SmallStreamedFile_Then_WriteAgain_Ensure_CacheHit_NoThro
 
             var cacheHits = 0;
             var cacheMisses = 0;
-            _storageRoot.Options.FileSystemStatistics.ChunkCache = new Progress<CacheAccessType>(x =>
+            _storageRoot.Options.FileSystemStatistics.ChunkCache = new InlineProgress<CacheAccessType>(x =>
             {
                 if (x == CacheAccessType.CacheHit)
-                    cacheHits++;
+                    Interlocked.Increment(ref cacheHits);
                 else if (x == CacheAccessType.CacheMiss)
-                    cacheMisses++;
+                    Interlocked.Increment(ref cacheMisses);
             });
 
             // Act
@@ -66,5 +68,17 @@ public async Task Write_SmallStreamedFile_Then_WriteAgain_Ensure_CacheHit_NoThro
             Encoding.UTF8.GetString(buffer).Should().BeEquivalentTo(dataString + dataString);
             cacheMisses.Should().Be(1);
         }
+
+        private sealed class InlineProgress<T> : IProgress<T>
+        {
+            private readonly Action<T> _handler;
+
+            public InlineProgress(Action<T> handler)
+            {
+                _handler = handler ?? throw new ArgumentNullException(nameof(handler));
+            }
+
+            public void Report(T value) => _handler(value);
+        }
     }
-}
+}