feat(batch14): complete group3 purge compact state and wave3 tests

dotnet/tests/ZB.MOM.NatsNet.Server.Tests/ImplBacklog/ConcurrencyTests2.Impltests.cs

@@ -92,6 +92,36 @@ public sealed partial class ConcurrencyTests2
         });
     }
 
+    [Fact] // T:2480
+    public void NoRaceFileStoreLargeMsgsAndFirstMatching_ShouldSucceed()
+    {
+        var cfg = DefaultStreamConfig();
+        cfg.Subjects = [">"];
+
+        WithStore((fs, _) =>
+        {
+            for (var i = 0; i < 4_000; i++)
+                fs.StoreMsg($"foo.bar.{i}", null, null, 0);
+            for (var i = 0; i < 4_000; i++)
+                fs.StoreMsg($"foo.baz.{i}", null, null, 0);
+
+            var blocks = InvokePrivate<int>(fs, "NumMsgBlocks");
+            blocks.ShouldBeGreaterThanOrEqualTo(1);
+
+            var start = fs.State().FirstSeq;
+            for (var seq = start; seq < start + 7_600; seq++)
+                fs.RemoveMsg(seq).Removed.ShouldBeTrue();
+
+            var sw = System.Diagnostics.Stopwatch.StartNew();
+            var (sm, _) = fs.LoadNextMsg("*.baz.*", true, start, null);
+            sw.Stop();
+
+            sm.ShouldNotBeNull();
+            sm!.Subject.ShouldContain(".baz.");
+            sw.ElapsedMilliseconds.ShouldBeLessThan(50);
+        }, cfg);
+    }
+
     private static void WithStore(Action<JetStreamFileStore, string> action, StreamConfig? cfg = null)
     {
         var root = NewRoot();
@@ -134,5 +164,15 @@ public sealed partial class ConcurrencyTests2
         method!.Invoke(target, args);
     }
 
+    private static T InvokePrivate<T>(object target, string methodName, params object[] args)
+    {
+        var method = target.GetType().GetMethod(methodName, BindingFlags.Instance | BindingFlags.NonPublic);
+        method.ShouldNotBeNull();
+        var result = method!.Invoke(target, args);
+        if (result == null)
+            return default!;
+        return (T)result;
+    }
+
     private static string NewRoot() => Path.Combine(Path.GetTempPath(), $"impl-fs-c2-{Guid.NewGuid():N}");
 }