diff --git a/src/ZB.MOM.WW.LmxOpcUa.Host/OpcUaService.cs b/src/ZB.MOM.WW.LmxOpcUa.Host/OpcUaService.cs
index b775e14..25fcd3a 100644
--- a/src/ZB.MOM.WW.LmxOpcUa.Host/OpcUaService.cs
+++ b/src/ZB.MOM.WW.LmxOpcUa.Host/OpcUaService.cs
@@ -22,11 +22,14 @@ namespace ZB.MOM.WW.LmxOpcUa.Host
         private readonly AppConfiguration _config;
         private readonly IMxProxy? _mxProxy;
         private readonly IGalaxyRepository? _galaxyRepository;
+        private readonly IMxAccessClient? _mxAccessClientOverride;
+        private readonly bool _hasMxAccessClientOverride;
 
         private CancellationTokenSource? _cts;
         private PerformanceMetrics? _metrics;
         private StaComThread? _staThread;
         private MxAccessClient? _mxAccessClient;
+        private IMxAccessClient? _mxAccessClientForWiring;
         private ChangeDetectionService? _changeDetection;
         private OpcUaServerHost? _serverHost;
         private LmxNodeManager? _nodeManager;
@@ -59,11 +62,14 @@ namespace ZB.MOM.WW.LmxOpcUa.Host
         /// <summary>
         /// Test constructor. Accepts injected dependencies.
         /// </summary>
-        internal OpcUaService(AppConfiguration config, IMxProxy? mxProxy, IGalaxyRepository? galaxyRepository)
+        internal OpcUaService(AppConfiguration config, IMxProxy? mxProxy, IGalaxyRepository? galaxyRepository,
+            IMxAccessClient? mxAccessClientOverride = null, bool hasMxAccessClientOverride = false)
         {
             _config = config;
             _mxProxy = mxProxy;
             _galaxyRepository = galaxyRepository;
+            _mxAccessClientOverride = mxAccessClientOverride;
+            _hasMxAccessClientOverride = hasMxAccessClientOverride;
         }
 
         public void Start()
@@ -87,7 +93,16 @@ namespace ZB.MOM.WW.LmxOpcUa.Host
                 _metrics = new PerformanceMetrics();
 
                 // Step 5: Create MxAccessClient → Connect
-                if (_mxProxy != null)
+                if (_hasMxAccessClientOverride)
+                {
+                    // Test path: use injected IMxAccessClient directly (skips STA thread + COM)
+                    _mxAccessClientForWiring = _mxAccessClientOverride;
+                    if (_mxAccessClientForWiring != null && _mxAccessClientForWiring.State != ConnectionState.Connected)
+                    {
+                        _mxAccessClientForWiring.ConnectAsync(_cts.Token).GetAwaiter().GetResult();
+                    }
+                }
+                else if (_mxProxy != null)
                 {
                     try
                     {
@@ -121,8 +136,8 @@ namespace ZB.MOM.WW.LmxOpcUa.Host
                 }
 
                 // Step 8: Create OPC UA server host + node manager
-                IMxAccessClient mxClient = _mxAccessClient ?? (IMxAccessClient)new NullMxAccessClient();
-                _serverHost = new OpcUaServerHost(_config.OpcUa, mxClient, _metrics);
+                var effectiveMxClient = (IMxAccessClient?)_mxAccessClient ?? _mxAccessClientForWiring ?? new NullMxAccessClient();
+                _serverHost = new OpcUaServerHost(_config.OpcUa, effectiveMxClient, _metrics);
 
                 // Step 9-10: Query hierarchy, start server, build address space
                 if (_galaxyRepository != null && _galaxyStats.DbConnected)
@@ -170,7 +185,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host
                 // Step 13: Dashboard
                 _healthCheck = new HealthCheckService();
                 _statusReport = new StatusReportService(_healthCheck, _config.Dashboard.RefreshIntervalSeconds);
-                _statusReport.SetComponents(_mxAccessClient, _metrics, _galaxyStats, _serverHost);
+                _statusReport.SetComponents(effectiveMxClient, _metrics, _galaxyStats, _serverHost);
 
                 if (_config.Dashboard.Enabled)
                 {
@@ -253,7 +268,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host
         }
 
         // Accessors for testing
-        internal IMxAccessClient? MxClient => _mxAccessClient;
+        internal IMxAccessClient? MxClient => (IMxAccessClient?)_mxAccessClient ?? _mxAccessClientForWiring;
         internal PerformanceMetrics? Metrics => _metrics;
         internal OpcUaServerHost? ServerHost => _serverHost;
         internal LmxNodeManager? NodeManagerInstance => _nodeManager;
diff --git a/src/ZB.MOM.WW.LmxOpcUa.Host/OpcUaServiceBuilder.cs b/src/ZB.MOM.WW.LmxOpcUa.Host/OpcUaServiceBuilder.cs
new file mode 100644
index 0000000..f728386
--- /dev/null
+++ b/src/ZB.MOM.WW.LmxOpcUa.Host/OpcUaServiceBuilder.cs
@@ -0,0 +1,123 @@
+using System.Collections.Generic;
+using ZB.MOM.WW.LmxOpcUa.Host.Configuration;
+using ZB.MOM.WW.LmxOpcUa.Host.Domain;
+
+namespace ZB.MOM.WW.LmxOpcUa.Host
+{
+    /// <summary>
+    /// Fluent builder for constructing OpcUaService with dependency overrides.
+    /// Used by integration tests to substitute fakes for COM/DB components.
+    /// </summary>
+    internal class OpcUaServiceBuilder
+    {
+        private AppConfiguration _config = new AppConfiguration();
+        private IMxProxy? _mxProxy;
+        private IGalaxyRepository? _galaxyRepository;
+        private IMxAccessClient? _mxAccessClient;
+        private bool _mxProxySet;
+        private bool _galaxyRepositorySet;
+        private bool _mxAccessClientSet;
+
+        public OpcUaServiceBuilder WithConfig(AppConfiguration config)
+        {
+            _config = config;
+            return this;
+        }
+
+        public OpcUaServiceBuilder WithOpcUaPort(int port)
+        {
+            _config.OpcUa.Port = port;
+            return this;
+        }
+
+        public OpcUaServiceBuilder WithGalaxyName(string name)
+        {
+            _config.OpcUa.GalaxyName = name;
+            return this;
+        }
+
+        public OpcUaServiceBuilder WithMxProxy(IMxProxy? proxy)
+        {
+            _mxProxy = proxy;
+            _mxProxySet = true;
+            return this;
+        }
+
+        public OpcUaServiceBuilder WithGalaxyRepository(IGalaxyRepository? repository)
+        {
+            _galaxyRepository = repository;
+            _galaxyRepositorySet = true;
+            return this;
+        }
+
+        /// <summary>
+        /// Override the MxAccessClient directly, skipping STA thread and COM interop entirely.
+        /// When set, the service will use this client instead of creating one from IMxProxy.
+        /// </summary>
+        public OpcUaServiceBuilder WithMxAccessClient(IMxAccessClient? client)
+        {
+            _mxAccessClient = client;
+            _mxAccessClientSet = true;
+            return this;
+        }
+
+        public OpcUaServiceBuilder WithHierarchy(List<GalaxyObjectInfo> hierarchy, List<GalaxyAttributeInfo> attributes)
+        {
+            if (!_galaxyRepositorySet)
+            {
+                var fake = new FakeBuilderGalaxyRepository();
+                _galaxyRepository = fake;
+                _galaxyRepositorySet = true;
+            }
+
+            if (_galaxyRepository is FakeBuilderGalaxyRepository fakeRepo)
+            {
+                fakeRepo.Hierarchy = hierarchy;
+                fakeRepo.Attributes = attributes;
+            }
+
+            return this;
+        }
+
+        public OpcUaServiceBuilder DisableDashboard()
+        {
+            _config.Dashboard.Enabled = false;
+            return this;
+        }
+
+        public OpcUaServiceBuilder DisableChangeDetection()
+        {
+            _config.GalaxyRepository.ChangeDetectionIntervalSeconds = int.MaxValue;
+            return this;
+        }
+
+        public OpcUaService Build()
+        {
+            return new OpcUaService(
+                _config,
+                _mxProxySet ? _mxProxy : null,
+                _galaxyRepositorySet ? _galaxyRepository : null,
+                _mxAccessClientSet ? _mxAccessClient : null,
+                _mxAccessClientSet);
+        }
+
+        /// <summary>
+        /// Internal fake repository used by WithHierarchy for convenience.
+        /// </summary>
+        private class FakeBuilderGalaxyRepository : IGalaxyRepository
+        {
+            public event System.Action? OnGalaxyChanged;
+            public List<GalaxyObjectInfo> Hierarchy { get; set; } = new();
+            public List<GalaxyAttributeInfo> Attributes { get; set; } = new();
+
+            public System.Threading.Tasks.Task<List<GalaxyObjectInfo>> GetHierarchyAsync(System.Threading.CancellationToken ct = default)
+                => System.Threading.Tasks.Task.FromResult(Hierarchy);
+            public System.Threading.Tasks.Task<List<GalaxyAttributeInfo>> GetAttributesAsync(System.Threading.CancellationToken ct = default)
+                => System.Threading.Tasks.Task.FromResult(Attributes);
+            public System.Threading.Tasks.Task<System.DateTime?> GetLastDeployTimeAsync(System.Threading.CancellationToken ct = default)
+                => System.Threading.Tasks.Task.FromResult<System.DateTime?>(System.DateTime.UtcNow);
+            public System.Threading.Tasks.Task<bool> TestConnectionAsync(System.Threading.CancellationToken ct = default)
+                => System.Threading.Tasks.Task.FromResult(true);
+        }
+    }
+}
diff --git a/tests/ZB.MOM.WW.LmxOpcUa.Tests/Helpers/OpcUaServerFixture.cs b/tests/ZB.MOM.WW.LmxOpcUa.Tests/Helpers/OpcUaServerFixture.cs
new file mode 100644
index 0000000..c66dee5
--- /dev/null
+++ b/tests/ZB.MOM.WW.LmxOpcUa.Tests/Helpers/OpcUaServerFixture.cs
@@ -0,0 +1,103 @@
+using System.Threading;
+using System.Threading.Tasks;
+using Xunit;
+using ZB.MOM.WW.LmxOpcUa.Host;
+
+namespace ZB.MOM.WW.LmxOpcUa.Tests.Helpers
+{
+    /// <summary>
+    /// xUnit fixture that manages an OpcUaService lifecycle with automatic port allocation.
+    /// Guarantees no port conflicts between parallel tests.
+    ///
+    /// Usage (per-test):
+    ///   var fixture = OpcUaServerFixture.WithFakes();
+    ///   await fixture.InitializeAsync();
+    ///   try { ... } finally { await fixture.DisposeAsync(); }
+    ///
+    /// Usage (skip COM entirely):
+    ///   var fixture = OpcUaServerFixture.WithFakeMxAccessClient();
+    /// </summary>
+    internal class OpcUaServerFixture : IAsyncLifetime
+    {
+        private static int _nextPort = 16000;
+
+        public OpcUaService Service { get; private set; } = null!;
+        public int OpcUaPort { get; }
+        public string EndpointUrl => $"opc.tcp://localhost:{OpcUaPort}/LmxOpcUa";
+
+        private readonly OpcUaServiceBuilder _builder;
+        private bool _started;
+
+        public OpcUaServerFixture(OpcUaServiceBuilder builder)
+        {
+            OpcUaPort = Interlocked.Increment(ref _nextPort);
+            _builder = builder;
+            _builder.WithOpcUaPort(OpcUaPort);
+            _builder.DisableDashboard();
+        }
+
+        /// <summary>
+        /// Creates fixture with FakeMxProxy + FakeGalaxyRepository (standard test data).
+        /// The STA thread and COM interop run against FakeMxProxy.
+        /// </summary>
+        public static OpcUaServerFixture WithFakes(
+            FakeMxProxy? proxy = null,
+            FakeGalaxyRepository? repo = null)
+        {
+            var p = proxy ?? new FakeMxProxy();
+            var r = repo ?? new FakeGalaxyRepository
+            {
+                Hierarchy = TestData.CreateStandardHierarchy(),
+                Attributes = TestData.CreateStandardAttributes()
+            };
+
+            var builder = new OpcUaServiceBuilder()
+                .WithMxProxy(p)
+                .WithGalaxyRepository(r)
+                .WithGalaxyName("TestGalaxy");
+
+            return new OpcUaServerFixture(builder);
+        }
+
+        /// <summary>
+        /// Creates fixture using FakeMxAccessClient directly — skips STA thread + COM entirely.
+        /// Fastest option for tests that don't need real COM interop.
+        /// </summary>
+        public static OpcUaServerFixture WithFakeMxAccessClient(
+            FakeMxAccessClient? mxClient = null,
+            FakeGalaxyRepository? repo = null)
+        {
+            var client = mxClient ?? new FakeMxAccessClient();
+            var r = repo ?? new FakeGalaxyRepository
+            {
+                Hierarchy = TestData.CreateStandardHierarchy(),
+                Attributes = TestData.CreateStandardAttributes()
+            };
+
+            var builder = new OpcUaServiceBuilder()
+                .WithMxAccessClient(client)
+                .WithGalaxyRepository(r)
+                .WithGalaxyName("TestGalaxy");
+
+            return new OpcUaServerFixture(builder);
+        }
+
+        public Task InitializeAsync()
+        {
+            Service = _builder.Build();
+            Service.Start();
+            _started = true;
+            return Task.CompletedTask;
+        }
+
+        public Task DisposeAsync()
+        {
+            if (_started)
+            {
+                try { Service.Stop(); }
+                catch { /* swallow cleanup errors */ }
+            }
+            return Task.CompletedTask;
+        }
+    }
+}
diff --git a/tests/ZB.MOM.WW.LmxOpcUa.Tests/Helpers/OpcUaServerFixtureTests.cs b/tests/ZB.MOM.WW.LmxOpcUa.Tests/Helpers/OpcUaServerFixtureTests.cs
new file mode 100644
index 0000000..7ca4187
--- /dev/null
+++ b/tests/ZB.MOM.WW.LmxOpcUa.Tests/Helpers/OpcUaServerFixtureTests.cs
@@ -0,0 +1,86 @@
+using System.Diagnostics;
+using System.Threading.Tasks;
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.LmxOpcUa.Host.Domain;
+
+namespace ZB.MOM.WW.LmxOpcUa.Tests.Helpers
+{
+    public class OpcUaServerFixtureTests
+    {
+        [Fact]
+        public async Task WithFakes_StartsAndStops()
+        {
+            var fixture = OpcUaServerFixture.WithFakes();
+            await fixture.InitializeAsync();
+
+            fixture.Service.ShouldNotBeNull();
+            fixture.Service.MxClient.ShouldNotBeNull();
+            fixture.Service.MxClient!.State.ShouldBe(ConnectionState.Connected);
+            fixture.Service.GalaxyStatsInstance.ShouldNotBeNull();
+            fixture.Service.GalaxyStatsInstance!.GalaxyName.ShouldBe("TestGalaxy");
+            fixture.OpcUaPort.ShouldBeGreaterThan(16000);
+            fixture.EndpointUrl.ShouldContain(fixture.OpcUaPort.ToString());
+
+            await fixture.DisposeAsync();
+        }
+
+        [Fact]
+        public async Task WithFakeMxAccessClient_SkipsCom()
+        {
+            var mxClient = new FakeMxAccessClient();
+            var fixture = OpcUaServerFixture.WithFakeMxAccessClient(mxClient);
+            await fixture.InitializeAsync();
+
+            fixture.Service.MxClient.ShouldBe(mxClient);
+            mxClient.State.ShouldBe(ConnectionState.Connected);
+
+            await fixture.DisposeAsync();
+        }
+
+        [Fact]
+        public async Task MultipleFixtures_GetUniquePortsAutomatically()
+        {
+            var fixture1 = OpcUaServerFixture.WithFakeMxAccessClient();
+            var fixture2 = OpcUaServerFixture.WithFakeMxAccessClient();
+
+            fixture1.OpcUaPort.ShouldNotBe(fixture2.OpcUaPort);
+
+            // Both can start without port conflicts
+            await fixture1.InitializeAsync();
+            await fixture2.InitializeAsync();
+
+            fixture1.Service.ShouldNotBeNull();
+            fixture2.Service.ShouldNotBeNull();
+
+            await fixture1.DisposeAsync();
+            await fixture2.DisposeAsync();
+        }
+
+        [Fact]
+        public async Task Shutdown_CompletesWithin30Seconds()
+        {
+            var fixture = OpcUaServerFixture.WithFakes();
+            await fixture.InitializeAsync();
+
+            var sw = Stopwatch.StartNew();
+            await fixture.DisposeAsync();
+            sw.Stop();
+
+            sw.Elapsed.TotalSeconds.ShouldBeLessThan(30);
+        }
+
+        [Fact]
+        public async Task WithFakes_BuildsAddressSpace()
+        {
+            var fixture = OpcUaServerFixture.WithFakes();
+            await fixture.InitializeAsync();
+
+            fixture.Service.GalaxyStatsInstance!.ObjectCount.ShouldBe(5);
+            fixture.Service.GalaxyStatsInstance.AttributeCount.ShouldBe(6);
+            fixture.Service.GalaxyStatsInstance.DbConnected.ShouldBe(true);
+
+            await fixture.DisposeAsync();
+        }
+    }
+}
diff --git a/tests/ZB.MOM.WW.LmxOpcUa.Tests/Helpers/TestData.cs b/tests/ZB.MOM.WW.LmxOpcUa.Tests/Helpers/TestData.cs
new file mode 100644
index 0000000..5a78985
--- /dev/null
+++ b/tests/ZB.MOM.WW.LmxOpcUa.Tests/Helpers/TestData.cs
@@ -0,0 +1,52 @@
+using System.Collections.Generic;
+using ZB.MOM.WW.LmxOpcUa.Host.Domain;
+
+namespace ZB.MOM.WW.LmxOpcUa.Tests.Helpers
+{
+    /// <summary>
+    /// Reusable test data matching the Galaxy hierarchy from gr/layout.md.
+    /// </summary>
+    public static class TestData
+    {
+        public static List<GalaxyObjectInfo> CreateStandardHierarchy()
+        {
+            return new List<GalaxyObjectInfo>
+            {
+                new GalaxyObjectInfo { GobjectId = 1, TagName = "DEV", ContainedName = "DEV", BrowseName = "DEV", ParentGobjectId = 0, IsArea = true },
+                new GalaxyObjectInfo { GobjectId = 2, TagName = "TestArea", ContainedName = "TestArea", BrowseName = "TestArea", ParentGobjectId = 1, IsArea = true },
+                new GalaxyObjectInfo { GobjectId = 3, TagName = "TestMachine_001", ContainedName = "TestMachine_001", BrowseName = "TestMachine_001", ParentGobjectId = 2, IsArea = false },
+                new GalaxyObjectInfo { GobjectId = 4, TagName = "DelmiaReceiver_001", ContainedName = "DelmiaReceiver", BrowseName = "DelmiaReceiver", ParentGobjectId = 3, IsArea = false },
+                new GalaxyObjectInfo { GobjectId = 5, TagName = "MESReceiver_001", ContainedName = "MESReceiver", BrowseName = "MESReceiver", ParentGobjectId = 3, IsArea = false },
+            };
+        }
+
+        public static List<GalaxyAttributeInfo> CreateStandardAttributes()
+        {
+            return new List<GalaxyAttributeInfo>
+            {
+                new GalaxyAttributeInfo { GobjectId = 3, TagName = "TestMachine_001", AttributeName = "MachineID", FullTagReference = "TestMachine_001.MachineID", MxDataType = 5, IsArray = false },
+                new GalaxyAttributeInfo { GobjectId = 3, TagName = "TestMachine_001", AttributeName = "MachineCode", FullTagReference = "TestMachine_001.MachineCode", MxDataType = 5, IsArray = false },
+                new GalaxyAttributeInfo { GobjectId = 4, TagName = "DelmiaReceiver_001", AttributeName = "DownloadPath", FullTagReference = "DelmiaReceiver_001.DownloadPath", MxDataType = 5, IsArray = false },
+                new GalaxyAttributeInfo { GobjectId = 4, TagName = "DelmiaReceiver_001", AttributeName = "JobStepNumber", FullTagReference = "DelmiaReceiver_001.JobStepNumber", MxDataType = 2, IsArray = false },
+                new GalaxyAttributeInfo { GobjectId = 5, TagName = "MESReceiver_001", AttributeName = "MoveInBatchID", FullTagReference = "MESReceiver_001.MoveInBatchID", MxDataType = 5, IsArray = false },
+                new GalaxyAttributeInfo { GobjectId = 5, TagName = "MESReceiver_001", AttributeName = "MoveInPartNumbers", FullTagReference = "MESReceiver_001.MoveInPartNumbers[]", MxDataType = 5, IsArray = true, ArrayDimension = 50 },
+            };
+        }
+
+        public static List<GalaxyObjectInfo> CreateMinimalHierarchy()
+        {
+            return new List<GalaxyObjectInfo>
+            {
+                new GalaxyObjectInfo { GobjectId = 1, TagName = "TestObj", BrowseName = "TestObj", ParentGobjectId = 0, IsArea = false }
+            };
+        }
+
+        public static List<GalaxyAttributeInfo> CreateMinimalAttributes()
+        {
+            return new List<GalaxyAttributeInfo>
+            {
+                new GalaxyAttributeInfo { GobjectId = 1, TagName = "TestObj", AttributeName = "TestAttr", FullTagReference = "TestObj.TestAttr", MxDataType = 5, IsArray = false }
+            };
+        }
+    }
+}