From a0edac81fb838dd0005d7893d26d4271db76932e Mon Sep 17 00:00:00 2001
From: Joseph Doherty <dohejw01@gmail.com>
Date: Wed, 25 Mar 2026 06:10:49 -0400
Subject: [PATCH] Add probe/stale tag monitoring tests

Cover the full probe staleness detection path that was previously
untested: stale probe forces reconnect, data changes prevent false
staleness, no-probe config skips staleness check, probe tag subscribed
on connect and protected from unsubscribe.

5 new tests, 184 total passing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 .../MxAccess/MxAccessClientMonitorTests.cs    | 76 +++++++++++++++++++
 .../MxAccessClientSubscriptionTests.cs        | 32 ++++++++
 2 files changed, 108 insertions(+)

diff --git a/tests/ZB.MOM.WW.LmxOpcUa.Tests/MxAccess/MxAccessClientMonitorTests.cs b/tests/ZB.MOM.WW.LmxOpcUa.Tests/MxAccess/MxAccessClientMonitorTests.cs
index 071b6c3..8ca1be1 100644
--- a/tests/ZB.MOM.WW.LmxOpcUa.Tests/MxAccess/MxAccessClientMonitorTests.cs
+++ b/tests/ZB.MOM.WW.LmxOpcUa.Tests/MxAccess/MxAccessClientMonitorTests.cs
@@ -68,5 +68,81 @@ namespace ZB.MOM.WW.LmxOpcUa.Tests.MxAccess
             await Task.Delay(200);
             client.Dispose();
         }
+
+        [Fact]
+        public async Task Monitor_ProbeStale_ForcesReconnect()
+        {
+            var config = new MxAccessConfiguration
+            {
+                ProbeTag = "TestProbe",
+                ProbeStaleThresholdSeconds = 2,
+                MonitorIntervalSeconds = 1,
+                AutoReconnect = true
+            };
+            var client = new MxAccessClient(_staThread, _proxy, config, _metrics);
+
+            await client.ConnectAsync();
+            client.StartMonitor();
+
+            // Wait long enough for probe to go stale (threshold=2s, monitor interval=1s)
+            // No data changes simulated → probe becomes stale → reconnect triggered
+            await Task.Delay(4000);
+
+            client.StopMonitor();
+            client.ReconnectCount.ShouldBeGreaterThan(0);
+            client.Dispose();
+        }
+
+        [Fact]
+        public async Task Monitor_ProbeDataChange_PreventsStaleReconnect()
+        {
+            var config = new MxAccessConfiguration
+            {
+                ProbeTag = "TestProbe",
+                ProbeStaleThresholdSeconds = 2,
+                MonitorIntervalSeconds = 1,
+                AutoReconnect = true
+            };
+            var client = new MxAccessClient(_staThread, _proxy, config, _metrics);
+
+            await client.ConnectAsync();
+            client.StartMonitor();
+
+            // Continuously simulate probe data changes to keep it fresh
+            for (int i = 0; i < 8; i++)
+            {
+                await Task.Delay(500);
+                _proxy.SimulateDataChangeByAddress("TestProbe", i, 192);
+            }
+
+            client.StopMonitor();
+            // Probe was kept fresh → no reconnect should have happened
+            client.ReconnectCount.ShouldBe(0);
+            client.State.ShouldBe(ConnectionState.Connected);
+            client.Dispose();
+        }
+
+        [Fact]
+        public async Task Monitor_NoProbeConfigured_NoFalseReconnect()
+        {
+            var config = new MxAccessConfiguration
+            {
+                ProbeTag = null, // No probe
+                MonitorIntervalSeconds = 1,
+                AutoReconnect = true
+            };
+            var client = new MxAccessClient(_staThread, _proxy, config, _metrics);
+
+            await client.ConnectAsync();
+            client.StartMonitor();
+
+            // Wait several monitor cycles — should stay connected with no reconnects
+            await Task.Delay(3000);
+
+            client.StopMonitor();
+            client.State.ShouldBe(ConnectionState.Connected);
+            client.ReconnectCount.ShouldBe(0);
+            client.Dispose();
+        }
     }
 }
diff --git a/tests/ZB.MOM.WW.LmxOpcUa.Tests/MxAccess/MxAccessClientSubscriptionTests.cs b/tests/ZB.MOM.WW.LmxOpcUa.Tests/MxAccess/MxAccessClientSubscriptionTests.cs
index c4e46ec..d5e5730 100644
--- a/tests/ZB.MOM.WW.LmxOpcUa.Tests/MxAccess/MxAccessClientSubscriptionTests.cs
+++ b/tests/ZB.MOM.WW.LmxOpcUa.Tests/MxAccess/MxAccessClientSubscriptionTests.cs
@@ -101,5 +101,37 @@ namespace ZB.MOM.WW.LmxOpcUa.Tests.MxAccess
             _proxy.SimulateDataChangeByAddress("TestTag.Attr", "value", 192);
             callbackInvoked.ShouldBe(true);
         }
+
+        [Fact]
+        public async Task ProbeTag_SubscribedOnConnect()
+        {
+            var proxy = new FakeMxProxy();
+            var config = new MxAccessConfiguration { ProbeTag = "TestProbe" };
+            var client = new MxAccessClient(_staThread, proxy, config, _metrics);
+
+            await client.ConnectAsync();
+
+            // Probe tag should be subscribed (present in proxy items)
+            proxy.Items.Values.ShouldContain("TestProbe");
+            client.Dispose();
+        }
+
+        [Fact]
+        public async Task ProbeTag_ProtectedFromUnsubscribe()
+        {
+            var proxy = new FakeMxProxy();
+            var config = new MxAccessConfiguration { ProbeTag = "TestProbe" };
+            var client = new MxAccessClient(_staThread, proxy, config, _metrics);
+
+            await client.ConnectAsync();
+            proxy.Items.Values.ShouldContain("TestProbe");
+
+            // Attempt to unsubscribe the probe tag — should be protected
+            await client.UnsubscribeAsync("TestProbe");
+
+            // Probe should still be in the proxy items (not removed)
+            proxy.Items.Values.ShouldContain("TestProbe");
+            client.Dispose();
+        }
     }
 }