A couple of minor cleanup issues applied.

Author: kzdev-net

Source/Src/KZDev.PerfUtils/MemoryStream/MemoryStreamSlim.cs

@@ -1179,7 +1179,7 @@ public override ValueTask WriteAsync (ReadOnlyMemory<byte> buffer, CancellationT
     public override byte[] GetBuffer ()
     {
         ThrowHelper.ThrowNotSupportedException_FeatureNotSupported();
-        return default;
+        return null;
     }
     //--------------------------------------------------------------------------------
 

Source/Tst/Shared/KZDev.PerfUtils.TestMocks.Shared/FileStreamMock.cs

@@ -1,6 +1,7 @@
 
 
 using System.Buffers;
+using System.Diagnostics;
 
 namespace KZDev.PerfUtils.Tests;
 
@@ -109,10 +110,10 @@ private void AdjustSuspendAsyncDelay (bool increment)
         // Use conditional compilation to check for negative async suspension count
         // instead of Debug.Assert to avoid creating a local variable in release builds
 #if DEBUG
-            int newCount = Interlocked.Decrement(ref _asyncSuspendCount);
-            if (newCount >= 0)
-                return;
-            Debug.Fail("The async suspension count has gone negative");
+        int newCount = Interlocked.Decrement(ref _asyncSuspendCount);
+        if (newCount >= 0)
+            return;
+        Debug.Fail("The async suspension count has gone negative");
 #else
         Interlocked.Decrement(ref _asyncSuspendCount);
 #endif