Merge hw5-661 (#661 MTConnect reconnect test waits on ReconnectAttempts, cancellable)

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.Tests/MTConnectSubscribeTests.cs

@@ -995,6 +995,16 @@ public sealed class MTConnectSubscribeTests
         client.SampleCallCount.ShouldBe(3);
     }
 
+    private static async Task WaitForReconnectAttemptsAboveAsync(MTConnectDriver driver, int floor, CancellationToken ct)
+    {
+        using var watchdog = CancellationTokenSource.CreateLinkedTokenSource(ct);
+        watchdog.CancelAfter(Watchdog);
+        while (driver.ReconnectAttempts <= floor)
+        {
+            await Task.Delay(5, watchdog.Token).ConfigureAwait(false);
+        }
+    }
+
     /// <summary>
     ///     …and the counter still accumulates when nothing is delivered, which is the case the
     ///     backoff exists for. Asserted as monotonic growth rather than an exact value, because the
@@ -1015,7 +1025,11 @@ public sealed class MTConnectSubscribeTests
             await client.WaitForSampleCallsAsync(3).WaitAsync(Watchdog, Ct);
             var early = driver.ReconnectAttempts;
 
-            await client.WaitForSampleCallsAsync(6).WaitAsync(Watchdog, Ct);
+            // Wait on the counter itself, not on a sample-call count: the pump advances it AFTER a
+            // call fails, and `early` may have been read late (already past the 6th call) under load,
+            // so a call-count barrier can observe the counter unchanged. The failure is sticky, so a
+            // working backoff keeps growing it; a frozen one never satisfies this within the watchdog.
+            await WaitForReconnectAttemptsAboveAsync(driver, early, Ct);
 
             early.ShouldBeGreaterThanOrEqualTo(2);
             driver.ReconnectAttempts.ShouldBeGreaterThan(early);
@@ -1065,7 +1079,11 @@ public sealed class MTConnectSubscribeTests
             await client.WaitForSampleCallsAsync(3).WaitAsync(Watchdog, Ct);
             var early = driver.ReconnectAttempts;
 
-            await client.WaitForSampleCallsAsync(6).WaitAsync(Watchdog, Ct);
+            // Wait on the counter itself, not on a sample-call count: the pump advances it AFTER a
+            // call fails, and `early` may have been read late (already past the 6th call) under load,
+            // so a call-count barrier can observe the counter unchanged. The failure is sticky, so a
+            // working backoff keeps growing it; a frozen one never satisfies this within the watchdog.
+            await WaitForReconnectAttemptsAboveAsync(driver, early, Ct);
 
             early.ShouldBeGreaterThanOrEqualTo(2);
             driver.ReconnectAttempts.ShouldBeGreaterThan(early);