test(s7): assert the stale handle is disposed, not just replaced, in the cancellation-reopen pins

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7.Tests/S7SpanReadParityTests.cs

@@ -473,12 +473,13 @@ public sealed class S7SpanReadParityTests
 
         await Should.ThrowAsync<OperationCanceledException>(async () => await reading);
 
-        // The reopen is the observable half of the contract: the desynced handle was discarded, so
-        // the next read builds a NEW connection rather than reusing it.
+        // The reopen is the observable half of the contract: the desynced handle was DISPOSED — not
+        // merely leaked behind a second connection — and the next read builds a new one.
         factory.HangReadBytes = false;
         var recovered = await driver.ReadAsync(refs, ct);
         recovered.ShouldAllBe(s => s.StatusCode == 0u);
         factory.CreatedPlcCount.ShouldBe(2);
+        factory.Plcs[0].Disposed.ShouldBeTrue();
     }
 
     /// <summary>
@@ -507,6 +508,7 @@ public sealed class S7SpanReadParityTests
         var recovered = await driver.ReadAsync(refs, ct);
         recovered.ShouldAllBe(s => s.StatusCode == 0u);
         factory.CreatedPlcCount.ShouldBe(2);
+        factory.Plcs[0].Disposed.ShouldBeTrue();
     }
 
     // ── Configurability ──────────────────────────────────────────────────────────────────
@@ -640,18 +642,30 @@ public sealed class S7SpanReadParityTests
         /// <summary>How many connections this factory has been asked to build — the reopen observable.</summary>
         public int CreatedPlcCount;
 
+        /// <summary>
+        ///     Every connection this factory built, in build order, so a test can assert what became
+        ///     of the STALE one — a driver that leaked the old handle and merely opened a second
+        ///     would satisfy <see cref="CreatedPlcCount"/> alone.
+        /// </summary>
+        public List<ImageS7Plc> Plcs { get; } = new();
+
         /// <inheritdoc />
         public IS7Plc Create(S7CpuType cpuType, string host, int port, short rack, short slot, TimeSpan timeout)
         {
             Interlocked.Increment(ref CreatedPlcCount);
-            return new ImageS7Plc(this);
+            var plc = new ImageS7Plc(this);
+            lock (Plcs) Plcs.Add(plc);
+            return plc;
         }
 
-        private sealed class ImageS7Plc(ImageS7PlcFactory owner) : IS7Plc
+        public sealed class ImageS7Plc(ImageS7PlcFactory owner) : IS7Plc
         {
             /// <inheritdoc />
             public bool IsConnected { get; private set; }
 
+            /// <summary>True once the driver has disposed this handle — the discard half of a reopen.</summary>
+            public bool Disposed { get; private set; }
+
             /// <inheritdoc />
             public Task OpenAsync(CancellationToken ct) { IsConnected = true; return Task.CompletedTask; }
 
@@ -771,7 +785,11 @@ public sealed class S7SpanReadParityTests
             public Task ReadStatusAsync(CancellationToken ct) => Task.CompletedTask;
 
             /// <inheritdoc />
-            public void Dispose() => IsConnected = false;
+            public void Dispose()
+            {
+                IsConnected = false;
+                Disposed = true;
+            }
         }
     }
 }