Retain fake worker fault diagnostics in test fixtures

src/ZB.MOM.WW.MxGateway.Tests/Gateway/GatewayEndToEndMultiSubscriberTests.cs

@@ -2,6 +2,7 @@ using Google.Protobuf.WellKnownTypes;
 using Grpc.Core;
 using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Options;
+using Xunit.Abstractions;
 using ZB.MOM.WW.MxGateway.Contracts;
 using ZB.MOM.WW.MxGateway.Contracts.Proto;
 using ZB.MOM.WW.MxGateway.Server.Configuration;
@@ -21,7 +22,7 @@ namespace ZB.MOM.WW.MxGateway.Tests.Gateway;
 /// the fake worker harness. Covers fan-out to two concurrent subscribers, independent
 /// cancellation isolation, and the per-session subscriber cap.
 /// </summary>
-public sealed class GatewayEndToEndMultiSubscriberTests
+public sealed class GatewayEndToEndMultiSubscriberTests(ITestOutputHelper output)
 {
     private static readonly TimeSpan TestTimeout = TimeSpan.FromSeconds(10);
     private const int ServerHandle = 3001;
@@ -37,7 +38,7 @@ public sealed class GatewayEndToEndMultiSubscriberTests
     public async Task StreamEvents_TwoSubscribers_BothReceiveAllEvents()
     {
         MultiEventFakeWorkerProcessLauncher launcher = new(EventCount);
-        await using MultiSubscriberGatewayServiceFixture fixture = new(launcher);
+        await using MultiSubscriberGatewayServiceFixture fixture = new(launcher, diagnosticOutput: output.WriteLine);
 
         OpenSessionReply openReply = await fixture.Service.OpenSession(
             new OpenSessionRequest
@@ -136,7 +137,7 @@ public sealed class GatewayEndToEndMultiSubscriberTests
     public async Task StreamEvents_OneSubscriberCancels_OtherContinuesReceivingEvents()
     {
         GatedEventFakeWorkerProcessLauncher launcher = new();
-        await using MultiSubscriberGatewayServiceFixture fixture = new(launcher);
+        await using MultiSubscriberGatewayServiceFixture fixture = new(launcher, diagnosticOutput: output.WriteLine);
 
         OpenSessionReply openReply = await fixture.Service.OpenSession(
             new OpenSessionRequest
@@ -254,7 +255,7 @@ public sealed class GatewayEndToEndMultiSubscriberTests
         // (EventSubscriberLimitReached) is only reachable when multi-subscriber mode is on.
         // Without it the service hits EventSubscriberAlreadyActive instead — also
         // ResourceExhausted, but for the wrong reason — masking a misconfiguration.
-        await using MultiSubscriberGatewayServiceFixture fixture = new(launcher, maxEventSubscribersPerSession: cap);
+        await using MultiSubscriberGatewayServiceFixture fixture = new(launcher, maxEventSubscribersPerSession: cap, diagnosticOutput: output.WriteLine);
 
         OpenSessionReply openReply = await fixture.Service.OpenSession(
             new OpenSessionRequest
@@ -413,20 +414,25 @@ public sealed class GatewayEndToEndMultiSubscriberTests
     {
         private readonly GatewayMetrics _metrics = new();
         private readonly SessionRegistry _registry = new();
+        private readonly FakeWorkerDiagnostics _diagnostics;
 
         /// <summary>Initializes a new instance of the <see cref="MultiSubscriberGatewayServiceFixture"/> class.</summary>
         /// <param name="launcher">Fake worker process launcher backing the session manager.</param>
+        /// <param name="diagnosticOutput">Safe metadata output sink.</param>
         /// <param name="maxEventSubscribersPerSession">Maximum concurrent event subscribers allowed per session.</param>
         public MultiSubscriberGatewayServiceFixture(
             IWorkerProcessLauncher launcher,
-            int maxEventSubscribersPerSession = 8)
+            int maxEventSubscribersPerSession = 8,
+            Action<string>? diagnosticOutput = null)
         {
+            _diagnostics = ((IDiagnosticFakeWorker)launcher).Diagnostics;
+            _diagnostics.SetOutput(diagnosticOutput);
             IOptions<GatewayOptions> options = Options.Create(CreateOptions(maxEventSubscribersPerSession));
             SessionWorkerClientFactory workerClientFactory = new(
                 launcher,
                 options,
                 _metrics,
-                NullLoggerFactory.Instance);
+                _diagnostics);
             SessionManager sessionManager = new(
                 _registry,
                 workerClientFactory,
@@ -499,13 +505,20 @@ public sealed class GatewayEndToEndMultiSubscriberTests
         /// <summary>Disposes every session in the registry and releases the fixture's metrics.</summary>
         /// <returns>A task that represents the asynchronous operation.</returns>
         public async ValueTask DisposeAsync()
+        {
+            // Session disposal and worker observation share the existing test budget.
+            // The observer consumes a late cleanup fault without replacing the primary failure.
+            _diagnostics.Track(DisposeSessionsAsync(), "teardown");
+            await _diagnostics.DrainAsync(TestTimeout).ConfigureAwait(false);
+            _metrics.Dispose();
+        }
+
+        private async Task DisposeSessionsAsync()
         {
             foreach (GatewaySession session in _registry.Snapshot())
             {
-                await session.DisposeAsync();
+                await session.DisposeAsync().ConfigureAwait(false);
             }
-
-            _metrics.Dispose();
         }
 
         private static GatewayOptions CreateOptions(int maxEventSubscribersPerSession) =>
@@ -540,7 +553,7 @@ public sealed class GatewayEndToEndMultiSubscriberTests
     /// command, then waits for shutdown. Events carry an indexed string value so the test can
     /// verify fan-out order across two subscribers.
     /// </summary>
-    private sealed class MultiEventFakeWorkerProcessLauncher(int eventCount) : IWorkerProcessLauncher
+    private sealed class MultiEventFakeWorkerProcessLauncher(int eventCount) : IWorkerProcessLauncher, IDiagnosticFakeWorker
     {
         public const int ProcessId = 7710;
 
@@ -549,12 +562,16 @@ public sealed class GatewayEndToEndMultiSubscriberTests
         /// <summary>Gets the task representing the fake worker's running background loop.</summary>
         public Task WorkerTask { get; private set; } = Task.CompletedTask;
 
+        /// <inheritdoc />
+        public FakeWorkerDiagnostics Diagnostics { get; } = new();
+
         /// <inheritdoc />
         public Task<WorkerProcessHandle> LaunchAsync(
             WorkerProcessLaunchRequest request,
             CancellationToken cancellationToken = default)
         {
             WorkerTask = RunWorkerAsync(request, cancellationToken);
+            Diagnostics.Track(WorkerTask);
 
             return Task.FromResult(new WorkerProcessHandle(
                 _process,
@@ -578,6 +595,7 @@ public sealed class GatewayEndToEndMultiSubscriberTests
             {
                 WorkerEnvelope envelope = await harness.ReadGatewayEnvelopeAsync(cancellationToken).ConfigureAwait(false);
 
+                Diagnostics.Received(envelope);
                 if (envelope.BodyCase == WorkerEnvelope.BodyOneofCase.WorkerShutdown)
                 {
                     await harness.SendShutdownAckAsync(cancellationToken: cancellationToken).ConfigureAwait(false);
@@ -630,7 +648,7 @@ public sealed class GatewayEndToEndMultiSubscriberTests
     /// deterministic. Call <see cref="StopEmitting"/> before closing the session so the
     /// worker loop exits cleanly and can process the shutdown envelope.
     /// </summary>
-    private sealed class GatedEventFakeWorkerProcessLauncher : IWorkerProcessLauncher
+    private sealed class GatedEventFakeWorkerProcessLauncher : IWorkerProcessLauncher, IDiagnosticFakeWorker
     {
         public const int ProcessId = 7720;
 
@@ -643,6 +661,9 @@ public sealed class GatewayEndToEndMultiSubscriberTests
         /// <summary>Gets the task representing the fake worker's running background loop.</summary>
         public Task WorkerTask { get; private set; } = Task.CompletedTask;
 
+        /// <inheritdoc />
+        public FakeWorkerDiagnostics Diagnostics { get; } = new();
+
         /// <summary>Releases the gate so the worker emits one event.</summary>
         public void AllowNextEvent() => _emitGate.Release();
 
@@ -662,6 +683,7 @@ public sealed class GatewayEndToEndMultiSubscriberTests
             CancellationToken cancellationToken = default)
         {
             WorkerTask = RunWorkerAsync(request, cancellationToken);
+            Diagnostics.Track(WorkerTask);
 
             return Task.FromResult(new WorkerProcessHandle(
                 _process,
@@ -717,6 +739,7 @@ public sealed class GatewayEndToEndMultiSubscriberTests
                     continue;
                 }
 
+                Diagnostics.Received(envelope);
                 if (envelope.BodyCase == WorkerEnvelope.BodyOneofCase.WorkerShutdown)
                 {
                     await harness.SendShutdownAckAsync(cancellationToken: cancellationToken).ConfigureAwait(false);