UA-.NETStandard/tests/Opc.Ua.Server.Tests/ReferenceServerTest.cs

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 *
 * OPC Foundation MIT License 1.00
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using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using BenchmarkDotNet.Attributes;
using Microsoft.Extensions.Logging;
using NUnit.Framework;
using Opc.Ua.Server.TestFramework;
using Opc.Ua.Test;
using Opc.Ua.Tests;
using Quickstarts.ReferenceServer;

namespace Opc.Ua.Server.Tests
{
    /// <summary>
    /// Test Reference Server.
    /// </summary>
    [TestFixture]
    [Category("Server")]
    [SetCulture("en-us")]
    [SetUICulture("en-us")]
    [NonParallelizable]
    [MemoryDiagnoser]
    [DisassemblyDiagnoser]
    public class ReferenceServerTests
    {
        private const double kMaxAge = 10000;
        private const uint kTimeoutHint = 10000;
        private const uint kQueueSize = 5;

        private const string kClientApplicationUri =
            "urn:localhost:opcfoundation.org:ReferenceServerTests";

        private static readonly int[] s_staticMatrixDimensions = [5, 5];

        private ITelemetryContext m_telemetry;
        private ServerFixture<ReferenceServer> m_fixture;
        private ReferenceServer m_server;
        private RequestHeader m_requestHeader;
        private SecureChannelContext m_secureChannelContext;
        private OperationLimits m_operationLimits = null!;
        private ArrayOf<ReferenceDescription> m_referenceDescriptions;
        private RandomSource m_random;
        private DataGenerator m_generator;
        private bool m_sessionClosed;

        /// <summary>
        /// Set up a Server fixture.
        /// </summary>
        [OneTimeSetUp]
        public async Task OneTimeSetUpAsync()
        {
            m_telemetry = NUnitTelemetryContext.Create();
            // start Ref server
            m_fixture = new ServerFixture<ReferenceServer>(t => new ReferenceServer(t))
            {
                AllNodeManagers = true,
                OperationLimits = true,
                DurableSubscriptionsEnabled = false,
                UseSamplingGroupsInReferenceNodeManager = false,
                AutoAccept = true
            };
            await m_fixture.LoadConfigurationAsync().ConfigureAwait(false);
            m_fixture.Config.ServerConfiguration!.UserTokenPolicies =
            [
                new UserTokenPolicy(UserTokenType.Anonymous),
                new UserTokenPolicy(UserTokenType.UserName)
            ];
            m_server = await m_fixture.StartAsync().ConfigureAwait(false);
        }

        /// <summary>
        /// Tear down the server fixture.
        /// </summary>
        [OneTimeTearDown]
        public async Task OneTimeTearDownAsync()
        {
            await m_fixture.StopAsync().ConfigureAwait(false);
            Thread.Sleep(1000);
        }

        /// <summary>
        /// Create a session for a test.
        /// </summary>
        [SetUp]
        public async Task SetUpAsync()
        {
            (m_requestHeader, m_secureChannelContext) = await m_server.CreateAndActivateSessionAsync(
                TestContext.CurrentContext.Test.Name,
                clientApplicationUri: kClientApplicationUri).ConfigureAwait(false);
            m_requestHeader.Timestamp = DateTimeUtc.Now;
            m_requestHeader.TimeoutHint = kTimeoutHint;
            m_random = new RandomSource();
            m_generator = new DataGenerator(m_random, m_telemetry);
        }

        /// <summary>
        /// Tear down the test session.
        /// </summary>
        [TearDown]
        public async Task TearDownAsync()
        {
            if (!m_sessionClosed)
            {
                m_requestHeader.Timestamp = DateTimeUtc.Now;
                await m_server.CloseSessionAsync(m_secureChannelContext, m_requestHeader, CancellationToken.None).ConfigureAwait(false);
                m_requestHeader = null!;
            }
        }

        /// <summary>
        /// Set up a Reference Server a session
        /// </summary>
        [GlobalSetup]
        public async Task GlobalSetupAsync()
        {
            // start Ref server
            m_fixture = new ServerFixture<ReferenceServer>(t => new ReferenceServer(t))
            {
                AllNodeManagers = true
            };
            m_server = await m_fixture.StartAsync(null!).ConfigureAwait(false);
            (m_requestHeader, m_secureChannelContext) = await m_server.CreateAndActivateSessionAsync("Bench").ConfigureAwait(false);
        }

        /// <summary>
        /// Tear down Server and the close the session.
        /// </summary>
        [GlobalCleanup]
        public async Task GlobalCleanupAsync()
        {
            await m_server.CloseSessionAsync(m_secureChannelContext, m_requestHeader, true, RequestLifetime.None).ConfigureAwait(false);
            await m_fixture.StopAsync().ConfigureAwait(false);
            Thread.Sleep(1000);
        }

        /// <summary>
        /// Test for expected exceptions.
        /// </summary>
        [Test]
        public async Task NoInvalidTimestampExceptionAsync()
        {
            // test that the server accepts an invalid timestamp
            m_requestHeader.Timestamp = DateTimeUtc.Now - TimeSpan.FromDays(30);
            await m_server.CloseSessionAsync(m_secureChannelContext, m_requestHeader, false, RequestLifetime.None).ConfigureAwait(false);
            m_sessionClosed = true;
        }

        /// <summary>
        /// Get Endpoints.
        /// </summary>
        [Test]
        public void GetEndpoints()
        {
            ArrayOf<EndpointDescription> endpoints = m_server.GetEndpoints();
            Assert.That(endpoints.IsNull, Is.False);
        }

        /// <summary>
        /// Get Operation limits.
        /// </summary>
        [Test]
        [Order(100)]
        public async Task GetOperationLimitsAsync()
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            ILogger logger = telemetry.CreateLogger<ReferenceServerTests>();

            ArrayOf<ReadValueId> readIdCollection =
            [
                new ReadValueId {
                    AttributeId = Attributes.Value,
                    NodeId = VariableIds.Server_ServerCapabilities_OperationLimits_MaxNodesPerRead
                },
                new ReadValueId {
                    AttributeId = Attributes.Value,
                    NodeId = VariableIds
                        .Server_ServerCapabilities_OperationLimits_MaxNodesPerHistoryReadData
                },
                new ReadValueId {
                    AttributeId = Attributes.Value,
                    NodeId = VariableIds
                        .Server_ServerCapabilities_OperationLimits_MaxNodesPerHistoryReadEvents
                },
                new ReadValueId {
                    AttributeId = Attributes.Value,
                    NodeId = VariableIds.Server_ServerCapabilities_OperationLimits_MaxNodesPerWrite
                },
                new ReadValueId {
                    AttributeId = Attributes.Value,
                    NodeId = VariableIds
                        .Server_ServerCapabilities_OperationLimits_MaxNodesPerHistoryUpdateData
                },
                new ReadValueId {
                    AttributeId = Attributes.Value,
                    NodeId = VariableIds
                        .Server_ServerCapabilities_OperationLimits_MaxNodesPerHistoryUpdateEvents
                },
                new ReadValueId {
                    AttributeId = Attributes.Value,
                    NodeId = VariableIds.Server_ServerCapabilities_OperationLimits_MaxNodesPerBrowse
                },
                new ReadValueId {
                    AttributeId = Attributes.Value,
                    NodeId = VariableIds
                        .Server_ServerCapabilities_OperationLimits_MaxMonitoredItemsPerCall
                },
                new ReadValueId {
                    AttributeId = Attributes.Value,
                    NodeId = VariableIds
                        .Server_ServerCapabilities_OperationLimits_MaxNodesPerNodeManagement
                },
                new ReadValueId {
                    AttributeId = Attributes.Value,
                    NodeId = VariableIds
                        .Server_ServerCapabilities_OperationLimits_MaxNodesPerRegisterNodes
                },
                new ReadValueId {
                    AttributeId = Attributes.Value,
                    NodeId =
                        VariableIds.Server_ServerCapabilities_OperationLimits_MaxNodesPerTranslateBrowsePathsToNodeIds
                },
                new ReadValueId {
                    AttributeId = Attributes.Value,
                    NodeId = VariableIds
                        .Server_ServerCapabilities_OperationLimits_MaxNodesPerMethodCall
                }
            ];

            var requestHeader = (RequestHeader)m_requestHeader.Clone();
            requestHeader.Timestamp = DateTimeUtc.Now;
            ReadResponse readResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                requestHeader,
                kMaxAge,
                TimestampsToReturn.Neither,
                readIdCollection,
                RequestLifetime.None).ConfigureAwait(false);
            ServerFixtureUtils.ValidateResponse(readResponse.ResponseHeader, readResponse.Results, readIdCollection);
            ServerFixtureUtils.ValidateDiagnosticInfos(
                readResponse.DiagnosticInfos,
                readResponse.Results,
                readResponse.ResponseHeader.StringTable,
                logger);

            ArrayOf<DataValue> results = readResponse.Results;
            Assert.That(results.IsNull, Is.False);
            Assert.That(results.Count, Is.EqualTo(readIdCollection.Count));

            m_operationLimits = new OperationLimits
            {
                MaxNodesPerRead = (uint)results[0].WrappedValue,
                MaxNodesPerHistoryReadData = (uint)results[1].WrappedValue,
                MaxNodesPerHistoryReadEvents = (uint)results[2].WrappedValue,
                MaxNodesPerWrite = (uint)results[3].WrappedValue,
                MaxNodesPerHistoryUpdateData = (uint)results[4].WrappedValue,
                MaxNodesPerHistoryUpdateEvents = (uint)results[5].WrappedValue,
                MaxNodesPerBrowse = (uint)results[6].WrappedValue,
                MaxMonitoredItemsPerCall = (uint)results[7].WrappedValue,
                MaxNodesPerNodeManagement = (uint)results[8].WrappedValue,
                MaxNodesPerRegisterNodes = (uint)results[9].WrappedValue,
                MaxNodesPerTranslateBrowsePathsToNodeIds = (uint)results[10].WrappedValue,
                MaxNodesPerMethodCall = (uint)results[11].WrappedValue
            };
        }

        /// <summary>
        /// Read node.
        /// </summary>
        [Test]
        [Benchmark]
        public async Task ReadAsync()
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            ILogger logger = telemetry.CreateLogger<ReferenceServerTests>();

            // Read
            RequestHeader requestHeader = m_requestHeader;
            requestHeader.Timestamp = DateTimeUtc.Now;
            var nodeId = new NodeId("Scalar_Simulation_Int32", 2);
            var nodesToRead = ServerFixtureUtils.AttributesIds.Keys
                .Select(attributeId => new ReadValueId { NodeId = nodeId, AttributeId = attributeId })
                .ToArrayOf();
            ReadResponse readResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                requestHeader,
                kMaxAge,
                TimestampsToReturn.Neither,
                nodesToRead, RequestLifetime.None).ConfigureAwait(false);
            ServerFixtureUtils.ValidateResponse(readResponse.ResponseHeader, readResponse.Results, nodesToRead);
            ServerFixtureUtils.ValidateDiagnosticInfos(
                readResponse.DiagnosticInfos,
                readResponse.Results,
                readResponse.ResponseHeader.StringTable,
                logger);
        }

        /// <summary>
        /// Read all nodes.
        /// </summary>
        [Test]
        public async Task ReadAllNodesAsync()
        {
            var serverTestServices = new ServerTestServices(m_server, m_secureChannelContext);
            if (m_operationLimits == null)
            {
                await GetOperationLimitsAsync().ConfigureAwait(false);
            }
            if (m_referenceDescriptions.IsNull)
            {
                m_referenceDescriptions = await CommonTestWorkers.BrowseFullAddressSpaceWorkerAsync(
                    serverTestServices,
                    m_requestHeader,
                    m_operationLimits).ConfigureAwait(false);
            }
            // Read all variables
            RequestHeader requestHeader = m_requestHeader;
            foreach (ReferenceDescription reference in m_referenceDescriptions.ToList())
            {
                requestHeader.Timestamp = DateTimeUtc.Now;
                var nodeId = ExpandedNodeId.ToNodeId(
                    reference.NodeId,
                    m_server.CurrentInstance.NamespaceUris);
                var nodesToRead = ServerFixtureUtils.AttributesIds.Keys
                    .Select(attributeId => new ReadValueId { NodeId = nodeId, AttributeId = attributeId })
                    .ToArrayOf();
                TestContext.Out.WriteLine("NodeId {0} {1}", reference.NodeId, reference.BrowseName);
                ReadResponse readResponse = await m_server.ReadAsync(
                    m_secureChannelContext,
                    requestHeader,
                    kMaxAge,
                    TimestampsToReturn.Both,
                    nodesToRead, RequestLifetime.None).ConfigureAwait(false);
                ServerFixtureUtils.ValidateResponse(readResponse.ResponseHeader, readResponse.Results, nodesToRead);
                ServerFixtureUtils.ValidateDiagnosticInfos(
                    readResponse.DiagnosticInfos,
                    readResponse.Results,
                    readResponse.ResponseHeader.StringTable,
                    serverTestServices.Logger);

                foreach (DataValue dataValue in readResponse.Results)
                {
                    TestContext.Out.WriteLine(" {0}", dataValue.ToString());
                }
            }
        }

        /// <summary>
        /// Write Node.
        /// </summary>
        [Test]
        [Benchmark]
        public async Task WriteAsync()
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            ILogger logger = telemetry.CreateLogger<ReferenceServerTests>();

            // Write
            RequestHeader requestHeader = m_requestHeader;
            requestHeader.Timestamp = DateTimeUtc.Now;
            var nodeId = new NodeId("Scalar_Simulation_Int32", 2);
            var nodesToWrite = ServerFixtureUtils.AttributesIds.Keys
                .Select(attributeId => new WriteValue
                {
                    NodeId = nodeId,
                    AttributeId = Attributes.Value,
                    Value = new DataValue(1234)
                })
                .ToArrayOf();
            WriteResponse writeResponse = await m_server.WriteAsync(
                m_secureChannelContext,
                requestHeader,
                nodesToWrite, RequestLifetime.None).ConfigureAwait(false);
            ServerFixtureUtils.ValidateResponse(writeResponse.ResponseHeader, writeResponse.Results, nodesToWrite);
            ServerFixtureUtils.ValidateDiagnosticInfos(
                writeResponse.DiagnosticInfos,
                writeResponse.Results,
                writeResponse.ResponseHeader.StringTable,
                logger);
        }

        /// <summary>
        /// Test that ReferenceNodeManager variables update their SourceTimestamp on read.
        /// </summary>
        [Test]
        [Order(340)]
        public async Task ReferenceNodeManagerVariablesUpdateTimestampOnReadAsync()
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            ILogger logger = telemetry.CreateLogger<ReferenceServerTests>();

            // Read a variable from the ReferenceNodeManager (namespace index 2)
            var nodeId = new NodeId("Scalar_Static_Byte", 2);
            ArrayOf<ReadValueId> nodesToRead =
            [
                new ReadValueId
                {
                    NodeId = nodeId,
                    AttributeId = Attributes.Value
                }
            ];

            // First read
            RequestHeader requestHeader = m_requestHeader;
            requestHeader.Timestamp = DateTimeUtc.Now;
            DateTimeUtc timeBeforeFirstRead = DateTimeUtc.Now;
            ReadResponse firstReadResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                requestHeader,
                kMaxAge,
                TimestampsToReturn.Both,
                nodesToRead,
                RequestLifetime.None).ConfigureAwait(false);

            Assert.That(firstReadResponse, Is.Not.Null);
            Assert.That(firstReadResponse.Results.IsNull, Is.False);
            Assert.That(firstReadResponse.Results.Count, Is.EqualTo(1));
            DataValue firstValue = firstReadResponse.Results[0];
            Assert.That(firstValue.StatusCode, Is.EqualTo(StatusCodes.Good));
            Assert.That(firstValue.SourceTimestamp.IsNull, Is.False);
            if (logger.IsEnabled(LogLevel.Information))
            {
                logger.LogInformation("First read - SourceTimestamp: {SourceTimestamp}, ServerTimestamp: {ServerTimestamp}",
                    firstValue.SourceTimestamp, firstValue.ServerTimestamp);
            }

            // Verify the timestamp is recent (not startup time)
            Assert.That((long)firstValue.SourceTimestamp, Is.GreaterThanOrEqualTo((long)timeBeforeFirstRead.SubtractMilliseconds(1000)),
                "SourceTimestamp should be close to the read time, not the server startup time");

            // Wait a bit to ensure time difference
            await Task.Delay(1500).ConfigureAwait(false);

            // Second read
            requestHeader.Timestamp = DateTimeUtc.Now;
            DateTimeUtc timeBeforeSecondRead = DateTimeUtc.Now;
            ReadResponse secondReadResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                requestHeader,
                kMaxAge,
                TimestampsToReturn.Both,
                nodesToRead,
                RequestLifetime.None).ConfigureAwait(false);

            Assert.That(secondReadResponse, Is.Not.Null);
            Assert.That(secondReadResponse.Results.IsNull, Is.False);
            Assert.That(secondReadResponse.Results.Count, Is.EqualTo(1));
            DataValue secondValue = secondReadResponse.Results[0];
            Assert.That(secondValue.StatusCode, Is.EqualTo(StatusCodes.Good));
            Assert.That(secondValue.SourceTimestamp.IsNull, Is.False);
            if (logger.IsEnabled(LogLevel.Information))
            {
                logger.LogInformation("Second read - SourceTimestamp: {SourceTimestamp}, ServerTimestamp: {ServerTimestamp}",
                    secondValue.SourceTimestamp, secondValue.ServerTimestamp);
            }

            // Verify the second timestamp is more recent than the first
            Assert.That((long)secondValue.SourceTimestamp, Is.GreaterThan((long)firstValue.SourceTimestamp),
                "SourceTimestamp should be updated on each read");

            // Verify the second timestamp is recent
            Assert.That((long)secondValue.SourceTimestamp, Is.GreaterThanOrEqualTo((long)timeBeforeSecondRead.SubtractMilliseconds(1000)),
                "SourceTimestamp should be close to the second read time");
        }

        /// <summary>
        /// Test that the ReferenceNodeManager SelectionList variable exposes its
        /// value.
        /// </summary>
        [Test]
        public async Task ReferenceNodeManagerSelectionListVariableAsync()
        {
            ushort namespaceIndex = (ushort)m_server.CurrentInstance.NamespaceUris.GetIndex(
                Quickstarts.ReferenceServer.Namespaces.ReferenceServer);

            var valueNodeId = new NodeId("DataAccess_SelectionList_Colors", namespaceIndex);
            var selectionsNodeId = new NodeId(
                "DataAccess_SelectionList_Colors_Selections",
                namespaceIndex);
            var descriptionsNodeId = new NodeId(
                "DataAccess_SelectionList_Colors_SelectionDescriptions",
                namespaceIndex);
            var restrictToListNodeId = new NodeId(
                "DataAccess_SelectionList_Colors_RestrictToList",
                namespaceIndex);

            ArrayOf<ReadValueId> nodesToRead =
            [
                new ReadValueId { NodeId = valueNodeId, AttributeId = Attributes.Value },
                new ReadValueId { NodeId = valueNodeId, AttributeId = Attributes.DataType },
                new ReadValueId { NodeId = selectionsNodeId, AttributeId = Attributes.Value },
                new ReadValueId { NodeId = selectionsNodeId, AttributeId = Attributes.DataType },
                new ReadValueId { NodeId = descriptionsNodeId, AttributeId = Attributes.Value },
                new ReadValueId { NodeId = restrictToListNodeId, AttributeId = Attributes.Value }
            ];

            RequestHeader requestHeader = m_requestHeader;
            requestHeader.Timestamp = DateTimeUtc.Now;
            ReadResponse readResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                requestHeader,
                kMaxAge,
                TimestampsToReturn.Both,
                nodesToRead,
                RequestLifetime.None).ConfigureAwait(false);

            Assert.That(readResponse, Is.Not.Null);
            Assert.That(readResponse.Results.IsNull, Is.False);
            Assert.That(readResponse.Results.Count, Is.EqualTo(nodesToRead.Count));

            DataValue value = readResponse.Results[0];
            Assert.That(value.StatusCode, Is.EqualTo(StatusCodes.Good));
            Assert.That(value.WrappedValue.GetString(), Is.EqualTo("Red"));

            Assert.That(
                readResponse.Results[1].WrappedValue.TryGetValue(out NodeId valueDataType),
                Is.True);
            Assert.That(valueDataType, Is.EqualTo(DataTypeIds.String));

            Assert.That(
                readResponse.Results[2].WrappedValue.TryGetValue(
                    out ArrayOf<string> selections),
                Is.True);
            Assert.That(selections, Has.Count.EqualTo(3));
            Assert.That(selections[0], Is.EqualTo("Red"));
            Assert.That(selections[1], Is.EqualTo("Green"));
            Assert.That(selections[2], Is.EqualTo("Blue"));
            Assert.That(
                readResponse.Results[3].WrappedValue.TryGetValue(out NodeId selectionsDataType),
                Is.True);
            Assert.That(selectionsDataType, Is.EqualTo(DataTypeIds.String));

            Assert.That(
                readResponse.Results[4].WrappedValue.TryGetValue(
                    out ArrayOf<LocalizedText> selectionDescriptions),
                Is.True);
            Assert.That(selectionDescriptions, Has.Count.EqualTo(3));
            Assert.That(selectionDescriptions[0].Text, Is.EqualTo("The color red"));
            Assert.That(readResponse.Results[5].WrappedValue.GetBoolean(), Is.True);

            ArrayOf<WriteValue> nodesToWrite =
            [
                new WriteValue
                {
                    NodeId = valueNodeId,
                    AttributeId = Attributes.Value,
                    Value = new DataValue("Green")
                },
                new WriteValue
                {
                    NodeId = valueNodeId,
                    AttributeId = Attributes.Value,
                    Value = new DataValue("Purple")
                },
                new WriteValue
                {
                    NodeId = valueNodeId,
                    AttributeId = Attributes.Value,
                    Value = new DataValue("Red")
                }
            ];
            WriteResponse writeResponse = await m_server.WriteAsync(
                m_secureChannelContext,
                requestHeader,
                nodesToWrite,
                RequestLifetime.None).ConfigureAwait(false);
            Assert.That(writeResponse.Results, Has.Count.EqualTo(nodesToWrite.Count));
            Assert.That(writeResponse.Results[0], Is.EqualTo(StatusCodes.Good));
            Assert.That(writeResponse.Results[1], Is.EqualTo(StatusCodes.BadOutOfRange));
            Assert.That(writeResponse.Results[2], Is.EqualTo(StatusCodes.Good));
        }

        /// <summary>
        /// Tests that the discrete DataAccess node seed values (TrueState/FalseState,
        /// EnumStrings, EnumValues, ValueAsText) baked into the NodeSet2 model are
        /// materialized at runtime by the source generator.
        /// </summary>
        [Test]
        public async Task ReferenceNodeManagerDiscreteSeedValuesAsync()
        {
            ushort namespaceIndex = (ushort)m_server.CurrentInstance.NamespaceUris.GetIndex(
                Quickstarts.ReferenceServer.Namespaces.ReferenceServer);

            var twoStateTrueId = new NodeId(
                "DataAccess_TwoStateDiscreteType_DataAccess_TwoStateDiscreteType_001_TrueState",
                namespaceIndex);
            var twoStateFalseId = new NodeId(
                "DataAccess_TwoStateDiscreteType_DataAccess_TwoStateDiscreteType_001_FalseState",
                namespaceIndex);
            var multiStateEnumStringsId = new NodeId(
                "DataAccess_MultiStateDiscreteType_DataAccess_MultiStateDiscreteType_001_EnumStrings",
                namespaceIndex);
            var multiStateValueEnumValuesId = new NodeId(
                "DataAccess_MultiStateValueDiscreteType_DataAccess_MultiStateValueDiscreteType_001_EnumValues",
                namespaceIndex);
            var multiStateValueAsTextId = new NodeId(
                "DataAccess_MultiStateValueDiscreteType_DataAccess_MultiStateValueDiscreteType_001_ValueAsText",
                namespaceIndex);

            ArrayOf<ReadValueId> nodesToRead =
            [
                new ReadValueId { NodeId = twoStateTrueId, AttributeId = Attributes.Value },
                new ReadValueId { NodeId = twoStateFalseId, AttributeId = Attributes.Value },
                new ReadValueId { NodeId = multiStateEnumStringsId, AttributeId = Attributes.Value },
                new ReadValueId { NodeId = multiStateValueEnumValuesId, AttributeId = Attributes.Value },
                new ReadValueId { NodeId = multiStateValueAsTextId, AttributeId = Attributes.Value }
            ];

            RequestHeader requestHeader = m_requestHeader;
            requestHeader.Timestamp = DateTimeUtc.Now;
            ReadResponse readResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                requestHeader,
                kMaxAge,
                TimestampsToReturn.Both,
                nodesToRead,
                RequestLifetime.None).ConfigureAwait(false);

            Assert.That(readResponse, Is.Not.Null);
            Assert.That(readResponse.Results.IsNull, Is.False);
            Assert.That(readResponse.Results.Count, Is.EqualTo(nodesToRead.Count));

            foreach (DataValue result in readResponse.Results)
            {
                Assert.That(result.StatusCode, Is.EqualTo(StatusCodes.Good));
            }

            Assert.That(
                readResponse.Results[0].WrappedValue.TryGetValue(out LocalizedText trueState),
                Is.True);
            Assert.That(trueState.Text, Is.EqualTo("red"));
            Assert.That(
                readResponse.Results[1].WrappedValue.TryGetValue(out LocalizedText falseState),
                Is.True);
            Assert.That(falseState.Text, Is.EqualTo("blue"));

            Assert.That(
                readResponse.Results[2].WrappedValue.TryGetValue(
                    out ArrayOf<LocalizedText> enumStrings),
                Is.True);
            Assert.That(enumStrings, Has.Count.EqualTo(3));
            Assert.That(enumStrings[0].Text, Is.EqualTo("open"));
            Assert.That(enumStrings[1].Text, Is.EqualTo("closed"));
            Assert.That(enumStrings[2].Text, Is.EqualTo("jammed"));

            Assert.That(
                readResponse.Results[3].WrappedValue.TryGetValue(
                    out ArrayOf<ExtensionObject> enumValues),
                Is.True);
            Assert.That(enumValues, Has.Count.EqualTo(3));
            Assert.That(
                enumValues[0].TryGetValue(out EnumValueType? firstEnumValue),
                Is.True);
            Assert.That(firstEnumValue!.Value, Is.Zero);
            Assert.That(firstEnumValue.DisplayName.Text, Is.EqualTo("open"));

            Assert.That(
                readResponse.Results[4].WrappedValue.TryGetValue(out LocalizedText valueAsText),
                Is.True);
            Assert.That(valueAsText.Text, Is.EqualTo("open"));
        }

        /// <summary>
        /// Tests that AccessLevelEx retains the same base access bits as AccessLevel.
        /// </summary>
        [TestCase("Scalar_Static_NonatomicReadWrite")]
        [TestCase("AccessRights_AccessAll_NonatomicReadWrite")]
        public async Task ReferenceNodeManagerNonatomicAccessLevelsAreConsistentAsync(string identifier)
        {
            ushort namespaceIndex = (ushort)m_server.CurrentInstance.NamespaceUris.GetIndex(
                Quickstarts.ReferenceServer.Namespaces.ReferenceServer);
            var nodeId = new NodeId(identifier, namespaceIndex);
            ArrayOf<ReadValueId> nodesToRead =
            [
                new ReadValueId { NodeId = nodeId, AttributeId = Attributes.AccessLevel },
                new ReadValueId { NodeId = nodeId, AttributeId = Attributes.UserAccessLevel },
                new ReadValueId { NodeId = nodeId, AttributeId = Attributes.AccessLevelEx }
            ];

            var requestHeader = (RequestHeader)m_requestHeader.Clone();
            requestHeader.Timestamp = DateTimeUtc.Now;
            ReadResponse response = await m_server.ReadAsync(
                m_secureChannelContext,
                requestHeader,
                kMaxAge,
                TimestampsToReturn.Neither,
                nodesToRead,
                RequestLifetime.None).ConfigureAwait(false);

            // the reference server grants StatusWrite and TimestampWrite on every
            // writable variable (OPC 10000-3 8.57).
            const byte expectedAccessLevel = (byte)(
                AccessLevels.CurrentReadOrWrite |
                AccessLevels.StatusWrite |
                AccessLevels.TimestampWrite);
            Assert.That(response.Results, Has.Count.EqualTo(nodesToRead.Count));
            Assert.That(response.Results[0].WrappedValue.GetByte(),
                Is.EqualTo(expectedAccessLevel));
            Assert.That(response.Results[1].WrappedValue.GetByte(),
                Is.EqualTo(expectedAccessLevel));

            uint accessLevelEx = response.Results[2].WrappedValue.GetUInt32();
            Assert.That(
                accessLevelEx & 0xff,
                Is.EqualTo((uint)expectedAccessLevel));
            Assert.That(
                accessLevelEx & (uint)AccessLevelExType.NonatomicRead,
                Is.EqualTo((uint)AccessLevelExType.NonatomicRead));
            Assert.That(
                accessLevelEx & (uint)AccessLevelExType.NonatomicWrite,
                Is.EqualTo((uint)AccessLevelExType.NonatomicWrite));
        }

        /// <summary>
        /// The ArrayItemType engineering units and axis definitions carry a UNECE unit, and the
        /// Float AnalogItemType has a non-empty EURange, so the CTT Engineering Units and
        /// PercentDeadband test cases do not skip the nodes.
        /// </summary>
        [Test]
        public async Task ReferenceNodeManagerDataAccessUnitsAndRangesAreConfiguredAsync()
        {
            ushort namespaceIndex = (ushort)m_server.CurrentInstance.NamespaceUris.GetIndex(
                Quickstarts.ReferenceServer.Namespaces.ReferenceServer);
            string[] arrayItems = ["YArray", "XYArray", "Image", "Cube", "NDimension"];
            var nodesToRead = new List<ReadValueId>();
            foreach (string item in arrayItems)
            {
                nodesToRead.Add(new ReadValueId
                {
                    NodeId = new NodeId(
                        $"DataAccess_ArrayItemType_DataAccess_ArrayItemType_{item}_EngineeringUnits",
                        namespaceIndex),
                    AttributeId = Attributes.Value
                });
            }
            nodesToRead.Add(new ReadValueId
            {
                NodeId = new NodeId(
                    "DataAccess_ArrayItemType_DataAccess_ArrayItemType_Cube_ZAxisDefinition",
                    namespaceIndex),
                AttributeId = Attributes.Value
            });
            nodesToRead.Add(new ReadValueId
            {
                NodeId = new NodeId(
                    "DataAccess_AnalogType_DataAccess_AnalogType_Float_EURange",
                    namespaceIndex),
                AttributeId = Attributes.Value
            });

            var requestHeader = (RequestHeader)m_requestHeader.Clone();
            requestHeader.Timestamp = DateTimeUtc.Now;
            ReadResponse response = await m_server.ReadAsync(
                m_secureChannelContext,
                requestHeader,
                kMaxAge,
                TimestampsToReturn.Neither,
                nodesToRead.ToArrayOf(),
                RequestLifetime.None).ConfigureAwait(false);

            Assert.That(response.Results, Has.Count.EqualTo(nodesToRead.Count));
            for (int ii = 0; ii < arrayItems.Length; ii++)
            {
                Assert.That(response.Results[ii].StatusCode, Is.EqualTo(StatusCodes.Good), arrayItems[ii]);
                Assert.That(response.Results[ii].WrappedValue.TryGetValue(out ExtensionObject extension), Is.True);
                Assert.That(extension.TryGetValue(out EUInformation? units), Is.True, arrayItems[ii]);
                Assert.That(units!.NamespaceUri, Is.EqualTo("http://www.opcfoundation.org/UA/units/un/cefact"));
                Assert.That(units.UnitId, Is.EqualTo(12890), arrayItems[ii]);
                Assert.That(units.DisplayName.Text, Is.EqualTo("mV"));
                Assert.That(units.Description.Text, Is.EqualTo("millivolt"));
            }

            DataValue axis = response.Results[arrayItems.Length];
            Assert.That(axis.WrappedValue.TryGetValue(out ExtensionObject axisExtension), Is.True);
            Assert.That(axisExtension.TryGetValue(out AxisInformation? axisInformation), Is.True);
            Assert.That(axisInformation!.EngineeringUnits.UnitId, Is.EqualTo(5457219));
            Assert.That(axisInformation.EngineeringUnits.DisplayName.Text, Is.EqualTo("s"));

            DataValue range = response.Results[arrayItems.Length + 1];
            Assert.That(range.WrappedValue.TryGetValue(out ExtensionObject rangeExtension), Is.True);
            Assert.That(rangeExtension.TryGetValue(out Range? euRange), Is.True);
            Assert.That(euRange!.High, Is.GreaterThan(euRange.Low));
        }

        /// <summary>
        /// Every static two-dimensional sample array is 5x5 so that the CTT multi-dimensional
        /// IndexRange test cases (for example "0,2:4") can use it.
        /// </summary>
        [Test]
        public async Task ReferenceNodeManagerStaticMatricesAreFiveByFiveAsync()
        {
            ushort namespaceIndex = (ushort)m_server.CurrentInstance.NamespaceUris.GetIndex(
                Quickstarts.ReferenceServer.Namespaces.ReferenceServer);
            string[] suffixes =
            [
                "Boolean", "Byte", "ByteString", "DateTime", "Double", "Duration", "Float", "Guid",
                "Int16", "Int32", "Int64", "Integer", "LocaleId", "LocalizedText", "NodeId", "Number",
                "QualifiedName", "SByte", "String", "UInt16", "UInt32", "UInt64", "UInteger", "UtcTime",
                "Variant", "XmlElement"
            ];
            var nodesToRead = new List<ReadValueId>();
            foreach (string suffix in suffixes)
            {
                var nodeId = new NodeId("Scalar_Static_Arrays2D_" + suffix, namespaceIndex);
                nodesToRead.Add(new ReadValueId { NodeId = nodeId, AttributeId = Attributes.ArrayDimensions });
                nodesToRead.Add(new ReadValueId { NodeId = nodeId, AttributeId = Attributes.Value });
            }

            var requestHeader = (RequestHeader)m_requestHeader.Clone();
            requestHeader.Timestamp = DateTimeUtc.Now;
            ReadResponse response = await m_server.ReadAsync(
                m_secureChannelContext,
                requestHeader,
                kMaxAge,
                TimestampsToReturn.Neither,
                nodesToRead.ToArrayOf(),
                RequestLifetime.None).ConfigureAwait(false);

            Assert.That(response.Results, Has.Count.EqualTo(nodesToRead.Count));
            for (int ii = 0; ii < suffixes.Length; ii++)
            {
                DataValue dimensions = response.Results[2 * ii];
                DataValue value = response.Results[(2 * ii) + 1];
                Assert.That(dimensions.StatusCode, Is.EqualTo(StatusCodes.Good), suffixes[ii]);
                Assert.That(dimensions.WrappedValue.TryGetValue(out ArrayOf<uint> arrayDimensions), Is.True, suffixes[ii]);
                Assert.That(arrayDimensions.ToArray(), Is.EqualTo(s_staticMatrixDimensions), suffixes[ii]);
                Assert.That(value.StatusCode, Is.EqualTo(StatusCodes.Good), suffixes[ii]);
                Assert.That(value.WrappedValue.TypeInfo.ValueRank, Is.EqualTo(ValueRanks.TwoDimensions), suffixes[ii]);
                Assert.That(value.WrappedValue.AsBoxedObject(), Is.InstanceOf<IConvertableToMatrix>(), suffixes[ii]);
                var matrix = ((IConvertableToMatrix)value.WrappedValue.AsBoxedObject())
                    .ToMatrix(value.WrappedValue.TypeInfo.BuiltInType);
                Assert.That(matrix.Dimensions, Is.EqualTo(s_staticMatrixDimensions), suffixes[ii]);
            }
        }

        /// <summary>
        /// DataAccess_DataItem_String does not provide the optional MinimumSamplingInterval attribute
        /// (CTT Base Info Server Capabilities 2 002.js).
        /// </summary>
        [Test]
        public async Task ReferenceNodeManagerDataItemHasNoMinimumSamplingIntervalAsync()
        {
            ushort namespaceIndex = (ushort)m_server.CurrentInstance.NamespaceUris.GetIndex(
                Quickstarts.ReferenceServer.Namespaces.ReferenceServer);
            var nodeId = new NodeId("DataAccess_DataItem_String", namespaceIndex);
            ArrayOf<ReadValueId> nodesToRead =
            [
                new ReadValueId { NodeId = nodeId, AttributeId = Attributes.MinimumSamplingInterval },
                new ReadValueId { NodeId = nodeId, AttributeId = Attributes.Value }
            ];

            var requestHeader = (RequestHeader)m_requestHeader.Clone();
            requestHeader.Timestamp = DateTimeUtc.Now;
            ReadResponse response = await m_server.ReadAsync(
                m_secureChannelContext,
                requestHeader,
                kMaxAge,
                TimestampsToReturn.Neither,
                nodesToRead,
                RequestLifetime.None).ConfigureAwait(false);

            Assert.That(response.Results, Has.Count.EqualTo(nodesToRead.Count));
            Assert.That(response.Results[0].StatusCode, Is.EqualTo(StatusCodes.BadAttributeIdInvalid));
            Assert.That(response.Results[1].StatusCode, Is.EqualTo(StatusCodes.Good));

            // the node can still be monitored; the sampling interval is revised as usual.
            var services = new ServerTestServices(m_server, m_secureChannelContext);
            CreateSubscriptionResponse subscription = await services.CreateSubscriptionAsync(
                requestHeader,
                100,
                100,
                10,
                0,
                true,
                0).ConfigureAwait(false);
            try
            {
                CreateMonitoredItemsResponse items = await services.CreateMonitoredItemsAsync(
                    requestHeader,
                    subscription.SubscriptionId,
                    TimestampsToReturn.Neither,
                    [
                        new MonitoredItemCreateRequest
                        {
                            ItemToMonitor = new ReadValueId { NodeId = nodeId, AttributeId = Attributes.Value },
                            MonitoringMode = MonitoringMode.Reporting,
                            RequestedParameters = new MonitoringParameters
                            {
                                ClientHandle = 1,
                                SamplingInterval = 0,
                                QueueSize = 1,
                                DiscardOldest = true
                            }
                        }
                    ]).ConfigureAwait(false);
                Assert.That(items.Results, Has.Count.EqualTo(1));
                Assert.That(items.Results[0].StatusCode, Is.EqualTo(StatusCodes.Good));
                Assert.That(items.Results[0].RevisedSamplingInterval, Is.GreaterThanOrEqualTo(0));
            }
            finally
            {
                await services.DeleteSubscriptionsAsync(
                    requestHeader,
                    [subscription.SubscriptionId]).ConfigureAwait(false);
            }
        }

        /// <summary>
        /// Scalar_Static_NonHistorizing_Boolean advertises HistoryRead access but is not
        /// historized; a HistoryRead returns Bad_HistoryOperationUnsupported (Part 4 §5.11.3,
        /// CTT Historical Access Read Raw Err-025.js).
        /// </summary>
        [Test]
        public async Task HistoryReadNonHistorizingNodeIsUnsupportedAsync()
        {
            ushort namespaceIndex = (ushort)m_server.CurrentInstance.NamespaceUris.GetIndex(
                Quickstarts.ReferenceServer.Namespaces.ReferenceServer);
            var nodeId = new NodeId("Scalar_Static_NonHistorizing_Boolean", namespaceIndex);
            ArrayOf<ReadValueId> nodesToRead =
            [
                new ReadValueId { NodeId = nodeId, AttributeId = Attributes.Historizing },
                new ReadValueId { NodeId = nodeId, AttributeId = Attributes.AccessLevel },
                new ReadValueId { NodeId = nodeId, AttributeId = Attributes.Value }
            ];

            var requestHeader = (RequestHeader)m_requestHeader.Clone();
            requestHeader.Timestamp = DateTimeUtc.Now;
            ReadResponse readResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                requestHeader,
                kMaxAge,
                TimestampsToReturn.Neither,
                nodesToRead,
                RequestLifetime.None).ConfigureAwait(false);

            Assert.That(readResponse.Results, Has.Count.EqualTo(nodesToRead.Count));
            Assert.That(readResponse.Results[0].WrappedValue.GetBoolean(), Is.False);
            Assert.That(
                readResponse.Results[1].WrappedValue.GetByte() & AccessLevels.HistoryRead,
                Is.EqualTo(AccessLevels.HistoryRead));
            Assert.That(readResponse.Results[2].StatusCode, Is.EqualTo(StatusCodes.Good));

            var historyReadDetails = new ReadRawModifiedDetails
            {
                StartTime = DateTimeUtc.Now.SubtractMilliseconds(60 * 60 * 1000),
                EndTime = DateTimeUtc.Now,
                NumValuesPerNode = 10,
                IsReadModified = false,
                ReturnBounds = false
            };

            requestHeader.Timestamp = DateTimeUtc.Now;
            HistoryReadResponse historyReadResponse = await m_server.HistoryReadAsync(
                m_secureChannelContext,
                requestHeader,
                new ExtensionObject(historyReadDetails),
                TimestampsToReturn.Source,
                false,
                [new HistoryReadValueId { NodeId = nodeId }],
                RequestLifetime.None).ConfigureAwait(false);

            Assert.That(historyReadResponse.Results, Has.Count.EqualTo(1));
            Assert.That(
                historyReadResponse.Results[0].StatusCode.Code,
                Is.EqualTo(StatusCodes.BadHistoryOperationUnsupported));
        }

        /// <summary>
        /// The Server object references nodes with HasComponent and with its subtype HasAddIn and
        /// has more than three references, so it can back the CTT setting
        /// "/Server Test/NodeIds/References/Has References of a ReferenceType and SubType"
        /// (View Basic 2 005/015/016/020, View Minimum Continuation Point 01 010/011).
        /// </summary>
        [Test]
        public async Task ServerObjectHasReferencesOfATypeAndItsSubtypeAsync()
        {
            var requestHeader = (RequestHeader)m_requestHeader.Clone();
            requestHeader.Timestamp = DateTimeUtc.Now;
            BrowseResponse response = await m_server.BrowseAsync(
                m_secureChannelContext,
                requestHeader,
                null,
                0,
                [
                    new BrowseDescription
                    {
                        NodeId = ObjectIds.Server,
                        BrowseDirection = BrowseDirection.Forward,
                        ReferenceTypeId = ReferenceTypeIds.HasComponent,
                        IncludeSubtypes = true,
                        ResultMask = (uint)BrowseResultMask.All
                    }
                ],
                RequestLifetime.None).ConfigureAwait(false);

            Assert.That(response.Results, Has.Count.EqualTo(1));
            ReferenceDescription[] references = response.Results[0].References.ToArray()!;
            Assert.That(
                references!.Count(r => r.ReferenceTypeId == ReferenceTypeIds.HasComponent),
                Is.GreaterThanOrEqualTo(3));
            Assert.That(
                references.Count(r => r.ReferenceTypeId == ReferenceTypeIds.HasAddIn),
                Is.GreaterThanOrEqualTo(1));
        }

        /// <summary>
        /// The Method and View node class sample nodes reference at least two nodes of their
        /// own NodeClass (CTT View Minimum Continuation Point 01 012.js, View Basic 2 018.js).
        /// </summary>
        [Test]
        [TestCase("Methods_Void", NodeClass.Method)]
        [TestCase("Views_Operations", NodeClass.View)]
        public async Task NodeClassSampleNodesReferenceTheirOwnNodeClassAsync(string identifier, NodeClass nodeClass)
        {
            ushort namespaceIndex = (ushort)m_server.CurrentInstance.NamespaceUris.GetIndex(
                Quickstarts.ReferenceServer.Namespaces.ReferenceServer);
            ArrayOf<BrowseDescription> nodesToBrowse =
            [
                new BrowseDescription
                {
                    NodeId = new NodeId(identifier, namespaceIndex),
                    BrowseDirection = BrowseDirection.Both,
                    ReferenceTypeId = ReferenceTypeIds.References,
                    IncludeSubtypes = true,
                    NodeClassMask = 0,
                    ResultMask = (uint)BrowseResultMask.All
                }
            ];

            var requestHeader = (RequestHeader)m_requestHeader.Clone();
            requestHeader.Timestamp = DateTimeUtc.Now;
            BrowseResponse response = await m_server.BrowseAsync(
                m_secureChannelContext,
                requestHeader,
                null,
                0,
                nodesToBrowse,
                RequestLifetime.None).ConfigureAwait(false);

            Assert.That(response.Results, Has.Count.EqualTo(1));
            Assert.That(response.Results[0].StatusCode, Is.EqualTo(StatusCodes.Good));
            ArrayOf<ReferenceDescription> references = response.Results[0].References;
            Assert.That(references.ToArray()!.Count(r => r.NodeClass == nodeClass), Is.GreaterThanOrEqualTo(2));
            Assert.That(references.ToArray()!.Count(r => r.NodeClass != nodeClass), Is.GreaterThanOrEqualTo(1));
        }

        /// <summary>
        /// Views can only be the source of hierarchical References (Part 3 §5.4), and the
        /// CTT (Base Info Core Structure 2 001.js) also rejects Views targeted by
        /// non-hierarchical References.
        /// </summary>
        [Test]
        [TestCase("Views_Operations")]
        [TestCase("Views_Engineering")]
        [TestCase("Views_Maintenance")]
        public async Task SampleViewsHaveNoNonHierarchicalReferencesAsync(string identifier)
        {
            ushort namespaceIndex = (ushort)m_server.CurrentInstance.NamespaceUris.GetIndex(
                Quickstarts.ReferenceServer.Namespaces.ReferenceServer);
            ArrayOf<BrowseDescription> nodesToBrowse =
            [
                new BrowseDescription
                {
                    NodeId = new NodeId(identifier, namespaceIndex),
                    BrowseDirection = BrowseDirection.Both,
                    ReferenceTypeId = ReferenceTypeIds.NonHierarchicalReferences,
                    IncludeSubtypes = true,
                    NodeClassMask = 0,
                    ResultMask = (uint)BrowseResultMask.All
                }
            ];

            var requestHeader = (RequestHeader)m_requestHeader.Clone();
            requestHeader.Timestamp = DateTimeUtc.Now;
            BrowseResponse response = await m_server.BrowseAsync(
                m_secureChannelContext,
                requestHeader,
                null,
                0,
                nodesToBrowse,
                RequestLifetime.None).ConfigureAwait(false);

            Assert.That(response.Results, Has.Count.EqualTo(1));
            Assert.That(response.Results[0].StatusCode, Is.EqualTo(StatusCodes.Good));
            Assert.That(response.Results[0].References.ToArray(), Is.Empty);
        }

        /// <summary>
        /// Test that the ReferenceNodeManager Currency variable exposes its value
        /// and its CurrencyUnit property.
        /// </summary>
        [Test]
        public async Task ReferenceNodeManagerCurrencyVariableAsync()
        {
            ushort namespaceIndex = (ushort)m_server.CurrentInstance.NamespaceUris.GetIndex(
                Quickstarts.ReferenceServer.Namespaces.ReferenceServer);

            var amountNodeId = new NodeId("DataAccess_Currency_Amount", namespaceIndex);
            var currencyUnitNodeId = new NodeId(
                "DataAccess_Currency_Amount_CurrencyUnit",
                namespaceIndex);

            ArrayOf<ReadValueId> nodesToRead =
            [
                new ReadValueId { NodeId = amountNodeId, AttributeId = Attributes.Value },
                new ReadValueId { NodeId = currencyUnitNodeId, AttributeId = Attributes.Value }
            ];

            RequestHeader requestHeader = m_requestHeader;
            requestHeader.Timestamp = DateTimeUtc.Now;
            ReadResponse readResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                requestHeader,
                kMaxAge,
                TimestampsToReturn.Both,
                nodesToRead,
                RequestLifetime.None).ConfigureAwait(false);

            Assert.That(readResponse, Is.Not.Null);
            Assert.That(readResponse.Results.IsNull, Is.False);
            Assert.That(readResponse.Results.Count, Is.EqualTo(2));

            DataValue amount = readResponse.Results[0];
            Assert.That(amount.StatusCode, Is.EqualTo(StatusCodes.Good));
            Assert.That(amount.WrappedValue.GetDouble(), Is.EqualTo(42.0));

            DataValue currencyUnit = readResponse.Results[1];
            Assert.That(currencyUnit.StatusCode, Is.EqualTo(StatusCodes.Good));
            Assert.That(currencyUnit.WrappedValue.TryGetValue(out ExtensionObject currencyUnitObject), Is.True);
            Assert.That(currencyUnitObject.TryGetValue(out CurrencyUnitType? unit), Is.True);
            Assert.That(unit!.NumericCode, Is.EqualTo(978));
            Assert.That(unit.Exponent, Is.EqualTo(2));
            Assert.That(unit.AlphabeticCode, Is.EqualTo("EUR"));

            using var stream = new MemoryStream();
            using (var encoder = new BinaryEncoder(
                stream,
                m_server.CurrentInstance.MessageContext,
                leaveOpen: true))
            {
                unit.Encode(encoder);
            }
            byte[] encoded = stream.ToArray();
            Assert.That(encoded, Has.Length.GreaterThan(2));
            Assert.That(encoded[0], Is.EqualTo(0xD2), "NumericCode low byte");
            Assert.That(encoded[1], Is.EqualTo(0x03), "NumericCode high byte");
            Assert.That(encoded[2], Is.EqualTo(0x02), "Exponent byte");
        }

        /// <summary>
        /// Test that ReferenceNodeManager array variables update their SourceTimestamp on read.
        /// </summary>
        [Test]
        public async Task ReferenceNodeManagerArrayVariablesUpdateTimestampOnReadAsync()
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            ILogger logger = telemetry.CreateLogger<ReferenceServerTests>();

            // Read an array variable from the ReferenceNodeManager (namespace index 2)
            var nodeId = new NodeId("Scalar_Static_Arrays_Byte", 2);
            ArrayOf<ReadValueId> nodesToRead =
            [
                new ReadValueId
                {
                    NodeId = nodeId,
                    AttributeId = Attributes.Value
                }
            ];

            // First read
            RequestHeader requestHeader = m_requestHeader;
            requestHeader.Timestamp = DateTimeUtc.Now;
            DateTimeUtc timeBeforeFirstRead = DateTimeUtc.Now;
            ReadResponse firstReadResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                requestHeader,
                kMaxAge,
                TimestampsToReturn.Both,
                nodesToRead,
                RequestLifetime.None).ConfigureAwait(false);

            Assert.That(firstReadResponse, Is.Not.Null);
            Assert.That(firstReadResponse.Results.IsNull, Is.False);
            Assert.That(firstReadResponse.Results.Count, Is.EqualTo(1));
            DataValue firstValue = firstReadResponse.Results[0];
            Assert.That(firstValue.StatusCode, Is.EqualTo(StatusCodes.Good));
            Assert.That(firstValue.SourceTimestamp.IsNull, Is.False);
            if (logger.IsEnabled(LogLevel.Information))
            {
                logger.LogInformation("Array First read - SourceTimestamp: {SourceTimestamp}, ServerTimestamp: {ServerTimestamp}",
                    firstValue.SourceTimestamp, firstValue.ServerTimestamp);
            }

            // Verify the timestamp is recent (not startup time)
            Assert.That((long)firstValue.SourceTimestamp, Is.GreaterThanOrEqualTo((long)timeBeforeFirstRead.SubtractMilliseconds(1000)),
                "Array SourceTimestamp should be close to the read time, not the server startup time");

            // Wait a bit to ensure time difference
            await Task.Delay(1500).ConfigureAwait(false);

            // Second read
            requestHeader.Timestamp = DateTimeUtc.Now;
            DateTimeUtc timeBeforeSecondRead = DateTimeUtc.Now;
            ReadResponse secondReadResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                requestHeader,
                kMaxAge,
                TimestampsToReturn.Both,
                nodesToRead,
                RequestLifetime.None).ConfigureAwait(false);

            Assert.That(secondReadResponse, Is.Not.Null);
            Assert.That(secondReadResponse.Results.IsNull, Is.False);
            Assert.That(secondReadResponse.Results.Count, Is.EqualTo(1));
            DataValue secondValue = secondReadResponse.Results[0];
            Assert.That(secondValue.StatusCode, Is.EqualTo(StatusCodes.Good));
            Assert.That(secondValue.SourceTimestamp.IsNull, Is.False);
            if (logger.IsEnabled(LogLevel.Information))
            {
                logger.LogInformation("Array Second read - SourceTimestamp: {SourceTimestamp}, ServerTimestamp: {ServerTimestamp}",
                    secondValue.SourceTimestamp, secondValue.ServerTimestamp);
            }

            // Verify the second timestamp is more recent than the first
            Assert.That((long)secondValue.SourceTimestamp, Is.GreaterThan((long)firstValue.SourceTimestamp),
                "Array SourceTimestamp should be updated on each read");

            // Verify the second timestamp is recent
            Assert.That((long)secondValue.SourceTimestamp, Is.GreaterThanOrEqualTo((long)timeBeforeSecondRead.SubtractMilliseconds(1000)),
                "Array SourceTimestamp should be close to the second read time");
        }

        /// <summary>
        /// Update static Nodes, read modify write.
        /// </summary>
        [Test]
        [Order(350)]
        public async Task ReadWriteUpdateNodesAsync()
        {
            // Nodes
            NamespaceTable namespaceUris = m_server.CurrentInstance.NamespaceUris;
            NodeId[] testSet =
            [
                .. CommonTestWorkers.NodeIdTestSetStatic
                    .Select(n => ExpandedNodeId.ToNodeId(n, namespaceUris))
            ];

            await UpdateValuesAsync(testSet).ConfigureAwait(false);
        }

        /// <summary>
        /// Browse full address space.
        /// </summary>
        [Test]
        [Order(400)]
        [Benchmark]
        public async Task BrowseFullAddressSpaceAsync()
        {
            var serverTestServices = new ServerTestServices(m_server, m_secureChannelContext);
            if (m_operationLimits == null)
            {
                await GetOperationLimitsAsync().ConfigureAwait(false);
            }
            m_referenceDescriptions = await CommonTestWorkers.BrowseFullAddressSpaceWorkerAsync(
                serverTestServices,
                m_requestHeader,
                m_operationLimits).ConfigureAwait(false);
        }

        /// <summary>
        /// Translate references.
        /// </summary>
        [Test]
        [Order(500)]
        [Benchmark]
        public async Task TranslateBrowsePathAsync()
        {
            var serverTestServices = new ServerTestServices(m_server, m_secureChannelContext);
            if (m_operationLimits == null)
            {
                await GetOperationLimitsAsync().ConfigureAwait(false);
            }
            if (m_referenceDescriptions.IsNull)
            {
                m_referenceDescriptions = await CommonTestWorkers.BrowseFullAddressSpaceWorkerAsync(
                    serverTestServices,
                    m_requestHeader,
                    m_operationLimits).ConfigureAwait(false);
            }
            _ = await CommonTestWorkers.TranslateBrowsePathWorkerAsync(
                serverTestServices,
                m_referenceDescriptions,
                m_requestHeader,
                m_operationLimits!).ConfigureAwait(false);
        }

        /// <summary>
        /// Create a subscription with a monitored item.
        /// Read a few notifications with Publish.
        /// Delete the monitored item and subscription.
        /// </summary>
        [Test]
        public async Task SubscriptionAsync()
        {
            var serverTestServices = new ServerTestServices(m_server, m_secureChannelContext);
            await CommonTestWorkers.SubscriptionTestAsync(serverTestServices, m_requestHeader).ConfigureAwait(false);
        }

        /// <summary>
        /// Create a single session + subscription and raise a single event on the server node.
        /// Validates all the event fields are properly received.
        /// </summary>
        [Test]
        public async Task ServerEventSubscribeTestAsync()
        {
            var services = new ServerTestServices(m_server, m_secureChannelContext);
            RequestHeader requestHeader = m_requestHeader;
            requestHeader.Timestamp = DateTime.UtcNow;

            CreateSubscriptionResponse createSubscriptionResponse = await services.CreateSubscriptionAsync(
                requestHeader,
                100,
                100,
                10,
                0,
                true,
                0).ConfigureAwait(false);

            uint subscriptionId = createSubscriptionResponse.SubscriptionId;

            // Build an event filter for the base event type.
            var eventFilter = new EventFilter();
            eventFilter.AddSelectClause(
                ObjectTypeIds.BaseEventType,
                QualifiedName.From(BrowseNames.EventId));
            eventFilter.AddSelectClause(
                ObjectTypeIds.BaseEventType,
                QualifiedName.From(BrowseNames.EventType));
            eventFilter.AddSelectClause(
                ObjectTypeIds.BaseEventType,
                QualifiedName.From(BrowseNames.SourceNode));
            eventFilter.AddSelectClause(
                ObjectTypeIds.BaseEventType,
                QualifiedName.From(BrowseNames.SourceName));
            eventFilter.AddSelectClause(
                ObjectTypeIds.BaseEventType,
                QualifiedName.From(BrowseNames.Time));
            eventFilter.AddSelectClause(
                ObjectTypeIds.BaseEventType,
                QualifiedName.From(BrowseNames.Message));
            eventFilter.AddSelectClause(
                ObjectTypeIds.BaseEventType,
                QualifiedName.From(BrowseNames.Severity));

            ArrayOf<MonitoredItemCreateRequest> monitoredItems = [
                new MonitoredItemCreateRequest
                {
                    ItemToMonitor = new ReadValueId { NodeId = ObjectIds.Server, AttributeId = Attributes.EventNotifier },
                    MonitoringMode = MonitoringMode.Reporting,
                    RequestedParameters = new MonitoringParameters
                    {
                        ClientHandle = 1,
                        SamplingInterval = 0,
                        QueueSize = 100,
                        DiscardOldest = true,
                        Filter = new ExtensionObject(eventFilter)
                    }
                }
            ];

            CreateMonitoredItemsResponse createItemsResponse = await services.CreateMonitoredItemsAsync(
                requestHeader,
                subscriptionId,
                TimestampsToReturn.Both,
                monitoredItems).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(createItemsResponse.ResponseHeader, createItemsResponse.Results, monitoredItems);
            Assert.AreEqual(1, createItemsResponse.Results.Count);
            Assert.IsTrue(StatusCode.IsGood(createItemsResponse.Results[0].StatusCode));

            // Generate event directly on the server
            IServerInternal serverInternal = m_server.CurrentInstance;
            ISystemContext serverContext = serverInternal.DefaultSystemContext;
            var e = new BaseEventState(null);
            const string eventMessage = "Integration Test Event";
            e.Initialize(
                serverContext,
                serverInternal.ServerObject,
                EventSeverity.Medium,
                new LocalizedText(eventMessage));
            serverInternal.ReportEvent(serverContext, e);

            // Wait for subscription to deliver the event
            await Task.Delay(200).ConfigureAwait(false);

            // Publish request to get the event notification
            var acknowledgements = new ArrayOf<SubscriptionAcknowledgement>();
            PublishResponse publishResponse = await services.PublishAsync(
                requestHeader,
                acknowledgements).ConfigureAwait(false);

            Assert.IsNotNull(publishResponse.NotificationMessage);
            Assert.IsNotNull(publishResponse.NotificationMessage.NotificationData);
            Assert.IsTrue(publishResponse.NotificationMessage.NotificationData.Count > 0);

            publishResponse.NotificationMessage.NotificationData[0].TryGetValue(out EventNotificationList? eventNotification);
            Assert.IsNotNull(eventNotification);
            Assert.IsTrue(eventNotification.Events.Count > 0);

            EventFieldList targetEvent = eventNotification.Events.ToList().FirstOrDefault(
                x => x.EventFields[5].TryGetValue(out LocalizedText lt) && lt.Text == eventMessage)!;
            Assert.IsNotNull(targetEvent, "Did not receive the target event.");

            ArrayOf<Variant> eventFields = targetEvent.EventFields;
            Assert.AreEqual(7, eventFields.Count); // we requested 7 fields in select clauses

            Assert.IsFalse(eventFields[0].IsNull); // EventId
            Assert.IsFalse(eventFields[1].IsNull); // EventType
            Assert.IsFalse(eventFields[2].IsNull); // SourceNode
            Assert.IsFalse(eventFields[3].IsNull); // SourceName
            Assert.IsFalse(eventFields[4].IsNull); // Time
            Assert.That(eventFields[5].TryGetValue(out LocalizedText receivedMessage), Is.True); // Message
            Assert.IsFalse(receivedMessage.IsNull);
            Assert.AreEqual(eventMessage, receivedMessage.Text);
            Assert.That(eventFields[6].TryGetValue(out ushort receiveSeverity), Is.True);
            Assert.AreEqual((ushort)EventSeverity.Medium, receiveSeverity); // Severity

            // Delete subscription
            await services.DeleteSubscriptionsAsync(
                requestHeader,
                [subscriptionId]).ConfigureAwait(false);
        }

        /// <summary>
        /// Create multiple sessions, each with a subscription.
        /// Close all sessions without deleting subscriptions (abandoning them).
        /// Concurrently delete the abandoned subscriptions through server-owned cleanup.
        /// Verifies that the concurrent dictionary backing abandoned subscriptions
        /// handles parallel access correctly (fix for issue #3612).
        /// </summary>
        [Test]
        public async Task DeleteAbandonedSubscriptionsConcurrentlyAsync()
        {
            const int sessionCount = 5;
            var subscriptionIds = new List<uint>();
            var subscriptionManager = (SubscriptionManager)m_server.CurrentInstance.SubscriptionManager;
            int originalSubscriptionCount = subscriptionManager.GetSubscriptions().Count;

            NamespaceTable namespaceUris = m_server.CurrentInstance.NamespaceUris;
            NodeId[] testSet =
            [
                .. CommonTestWorkers.NodeIdTestSetStatic
                        .Select(n => ExpandedNodeId.ToNodeId(n, namespaceUris))
            ];

            // Create multiple sessions, each with a subscription, then close
            // the session without deleting subscriptions so they become abandoned.
            for (int i = 0; i < sessionCount; i++)
            {
                (RequestHeader header, SecureChannelContext context) =
                    await m_server.CreateAndActivateSessionAsync($"AbandonSession_{i}")
                        .ConfigureAwait(false);

                var services = new ServerTestServices(m_server, context);
                header.Timestamp = DateTimeUtc.Now;
                ArrayOf<uint> ids = await CommonTestWorkers.CreateSubscriptionForTransferAsync(
                    services, header, testSet, kQueueSize, -1).ConfigureAwait(false);
                subscriptionIds.AddRange(ids.ToList());

                // Close session without deleting subscriptions - makes them abandoned
                header.Timestamp = DateTimeUtc.Now;
                await m_server.CloseSessionAsync(context, header, false, RequestLifetime.None)
                    .ConfigureAwait(false);
            }

            Assert.That(subscriptionIds, Has.Count.EqualTo(sessionCount));
            Assert.That(subscriptionIds, Is.Unique);
            foreach (uint id in subscriptionIds)
            {
                Assert.That(subscriptionManager.TryGetSubscription(id, out ISubscription? subscription), Is.True);
                Assert.That(subscription!.Session, Is.Null);
            }
            Assert.That(subscriptionManager.CaptureAbandonedPublishTimerSnapshot()
                .Select(subscription => subscription.Id), Is.SupersetOf(subscriptionIds));

            // A session cannot delete another session's abandoned subscription.
            // Server-owned cleanup uses the same null context as ServerInternalData.
            var deleteStart = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
            Task<StatusCode>[] deleteTasks =
            [
                .. subscriptionIds.Select(async id =>
                {
                    await deleteStart.Task.ConfigureAwait(false);
                    return await subscriptionManager.DeleteSubscriptionAsync(null!, id).ConfigureAwait(false);
                })
            ];
            deleteStart.SetResult(true);
            StatusCode[] results = await Task.WhenAll(deleteTasks).ConfigureAwait(false);

            Assert.That(results, Has.Length.EqualTo(sessionCount));
            foreach (StatusCode result in results)
            {
                Assert.That(result, Is.EqualTo(StatusCodes.Good));
            }
            foreach (uint id in subscriptionIds)
            {
                Assert.That(subscriptionManager.TryGetSubscription(id, out _), Is.False);
            }
            Assert.That(subscriptionManager.GetSubscriptions(), Has.Count.EqualTo(originalSubscriptionCount));
            Assert.That(subscriptionManager.CaptureAbandonedPublishTimerSnapshot()
                .Select(subscription => subscription.Id).Intersect(subscriptionIds), Is.Empty);
        }

        /// <summary>
        /// Create a secondary Session.
        /// Create a subscription with a monitored item.
        /// Close session, but do not delete subscriptions.
        /// Transfer subscription from closed session to the other.
        /// </summary>
        [Theory]
        public async Task TransferSubscriptionSessionClosedAsync(bool sendInitialData, bool useSecurity)
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();

            var serverTestServices = new ServerTestServices(m_server, m_secureChannelContext);
            (RequestHeader transferRequestHeader, SecureChannelContext transferContext) = await m_server.CreateAndActivateSessionAsync(
                "ClosedSession",
                useSecurity,
                clientApplicationUri: kClientApplicationUri).ConfigureAwait(false);
            NamespaceTable namespaceUris = m_server.CurrentInstance.NamespaceUris;
            NodeId[] testSet =
            [
                .. CommonTestWorkers.NodeIdTestSetStatic
                        .Select(n => ExpandedNodeId.ToNodeId(n, namespaceUris))
            ];
            transferRequestHeader.Timestamp = DateTimeUtc.Now;
            serverTestServices.SecureChannelContext = transferContext;
            ArrayOf<uint> subscriptionIds = await CommonTestWorkers.CreateSubscriptionForTransferAsync(
                serverTestServices,
                transferRequestHeader,
                testSet,
                kQueueSize,
                -1).ConfigureAwait(false);

            transferRequestHeader.Timestamp = DateTimeUtc.Now;
            await m_server.CloseSessionAsync(transferContext, transferRequestHeader, false, RequestLifetime.None).ConfigureAwait(false);

            //restore security context, transfer abandoned subscription
            serverTestServices.SecureChannelContext = m_secureChannelContext;
            await CommonTestWorkers.TransferSubscriptionTestAsync(
                serverTestServices,
                m_requestHeader,
                subscriptionIds,
                sendInitialData,
                !useSecurity).ConfigureAwait(false);

            if (useSecurity)
            {
                // subscription was deleted, expect 'BadNoSubscription'
                ServiceResultException sre = Assert.ThrowsAsync<ServiceResultException>(async () =>
                {
                    m_requestHeader.Timestamp = DateTimeUtc.Now;
                    await CommonTestWorkers.VerifySubscriptionTransferredAsync(
                        serverTestServices,
                        m_requestHeader,
                        subscriptionIds,
                        true).ConfigureAwait(false);
                });
                Assert.That(
                    sre.StatusCode,
                    Is.EqualTo(StatusCodes.BadNoSubscription));
            }
        }

        /// <summary>
        /// Create a subscription with a monitored item.
        /// Create a secondary Session.
        /// Transfer subscription with a monitored item from one session to the other.
        /// </summary>
        [Theory]
        public async Task TransferSubscriptionAsync(bool sendInitialData, bool useSecurity)
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();

            var serverTestServices = new ServerTestServices(m_server, m_secureChannelContext);

            NamespaceTable namespaceUris = m_server.CurrentInstance.NamespaceUris;
            NodeId[] testSet =
            [
                .. CommonTestWorkers.NodeIdTestSetStatic
                        .Select(n => ExpandedNodeId.ToNodeId(n, namespaceUris))
            ];
            ArrayOf<uint> subscriptionIds = await CommonTestWorkers.CreateSubscriptionForTransferAsync(
                serverTestServices,
                m_requestHeader,
                testSet,
                kQueueSize,
                -1).ConfigureAwait(false);

            (RequestHeader transferRequestHeader, SecureChannelContext transferSecurityContext) = await m_server.CreateAndActivateSessionAsync(
                "TransferSession",
                useSecurity,
                clientApplicationUri: kClientApplicationUri).ConfigureAwait(false);
            serverTestServices.SecureChannelContext = transferSecurityContext;
            await CommonTestWorkers.TransferSubscriptionTestAsync(
                serverTestServices,
                transferRequestHeader,
                subscriptionIds,
                sendInitialData,
                !useSecurity).ConfigureAwait(false);

            if (useSecurity)
            {
                //restore security context
                serverTestServices.SecureChannelContext = m_secureChannelContext;
                await CommonTestWorkers.VerifySubscriptionTransferredAsync(
                    serverTestServices,
                    m_requestHeader,
                    subscriptionIds,
                    true).ConfigureAwait(false);
            }

            transferRequestHeader.Timestamp = DateTimeUtc.Now;
            await m_server.CloseSessionAsync(transferSecurityContext, transferRequestHeader, true, RequestLifetime.None).ConfigureAwait(false);
        }

        /// <summary>
        /// Verifies that an anonymous Subscription cannot be transferred to a
        /// Session with a different client ApplicationUri.
        /// </summary>
        [Test]
        public async Task TransferAnonymousSubscriptionWithDifferentApplicationUriDeniedAsync()
        {
            var serverTestServices = new ServerTestServices(m_server, m_secureChannelContext);
            NamespaceTable namespaceUris = m_server.CurrentInstance.NamespaceUris;
            NodeId[] testSet =
            [
                .. CommonTestWorkers.NodeIdTestSetStatic
                    .Select(n => ExpandedNodeId.ToNodeId(n, namespaceUris))
            ];
            ArrayOf<uint> subscriptionIds = await CommonTestWorkers.CreateSubscriptionForTransferAsync(
                serverTestServices,
                m_requestHeader,
                testSet,
                kQueueSize,
                -1).ConfigureAwait(false);

            (RequestHeader transferRequestHeader, SecureChannelContext transferSecurityContext) =
                await m_server.CreateAndActivateSessionAsync(
                    "TransferSessionDifferentApplicationUri",
                    useSecurity: true,
                    clientApplicationUri:
                        "urn:localhost:opcfoundation.org:DifferentServerFixtureClient")
                    .ConfigureAwait(false);
            try
            {
                serverTestServices.SecureChannelContext = transferSecurityContext;
                await CommonTestWorkers.TransferSubscriptionTestAsync(
                    serverTestServices,
                    transferRequestHeader,
                    subscriptionIds,
                    sendInitialData: false,
                    expectAccessDenied: true).ConfigureAwait(false);
            }
            finally
            {
                transferRequestHeader.Timestamp = DateTimeUtc.Now;
                await m_server.CloseSessionAsync(
                    transferSecurityContext,
                    transferRequestHeader,
                    true,
                    RequestLifetime.None).ConfigureAwait(false);
            }
        }

        /// <summary>
        /// Create a subscription with a monitored item.
        /// Call ResendData.
        /// Ensure only a single value per monitored item is returned after ResendData was called.
        /// </summary>
        [Test]
        [TestCase(true, kQueueSize)]
        [TestCase(false, kQueueSize)]
        [TestCase(true, 0U)]
        [TestCase(false, 0U)]
        public async Task ResendDataAsync(bool updateValues, uint queueSize)
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();

            var serverTestServices = new ServerTestServices(m_server, m_secureChannelContext);

            NamespaceTable namespaceUris = m_server.CurrentInstance.NamespaceUris;
            var testSetCollection = CommonTestWorkers
                .NodeIdTestSetStatic.Select(n => ExpandedNodeId.ToNodeId(n, namespaceUris))
                .ToList();
            testSetCollection.AddRange(
                CommonTestWorkers.NodeIdTestDataSetStatic
                    .Select(n => ExpandedNodeId.ToNodeId(n, namespaceUris)));
            NodeId[] testSet = [.. testSetCollection];

            //Re-use method CreateSubscriptionForTransfer to create a subscription
            ArrayOf<uint> subscriptionIds = await CommonTestWorkers.CreateSubscriptionForTransferAsync(
                serverTestServices,
                m_requestHeader,
                testSet,
                queueSize,
                0).ConfigureAwait(false);

            (RequestHeader resendDataRequestHeader, SecureChannelContext resendDataSecurityContext) =
                await m_server.CreateAndActivateSessionAsync("ResendData").ConfigureAwait(false);

            serverTestServices.SecureChannelContext = m_secureChannelContext;
            // After the ResendData call there will be data to publish again
            ArrayOf<CallMethodRequest> nodesToCall = await ResendDataCallAsync(
                StatusCodes.Good,
                subscriptionIds).ConfigureAwait(false);

            Thread.Sleep(1000);

            // Make sure publish queue becomes empty by consuming it
            Assert.That(subscriptionIds.Count, Is.EqualTo(1));

            // Issue a Publish request
            m_requestHeader.Timestamp = DateTimeUtc.Now;
            ArrayOf<SubscriptionAcknowledgement> acknowledgements = [];
            PublishResponse publishResponse = await serverTestServices.PublishAsync(
                m_requestHeader,
                acknowledgements).ConfigureAwait(false);

            Assert.That(publishResponse.ResponseHeader.ServiceResult, Is.EqualTo(StatusCodes.Good));
            ServerFixtureUtils.ValidateResponse(publishResponse.ResponseHeader);
            ServerFixtureUtils.ValidateDiagnosticInfos(
                publishResponse.DiagnosticInfos,
                acknowledgements,
                publishResponse.ResponseHeader.StringTable,
                serverTestServices.Logger);
            Assert.That(publishResponse.SubscriptionId, Is.EqualTo(subscriptionIds[0]));
            Assert.That(publishResponse.NotificationMessage.NotificationData.Count, Is.EqualTo(1));

            // Validate nothing to publish a few times
            const int timesToCallPublish = 3;
            for (int i = 0; i < timesToCallPublish; i++)
            {
                m_requestHeader.Timestamp = DateTimeUtc.Now;
                publishResponse = await serverTestServices.PublishAsync(
                    m_requestHeader,
                    acknowledgements).ConfigureAwait(false);

                Assert.That(publishResponse.ResponseHeader.ServiceResult, Is.EqualTo(StatusCodes.Good));
                ServerFixtureUtils.ValidateResponse(publishResponse.ResponseHeader);
                ServerFixtureUtils.ValidateDiagnosticInfos(
                    publishResponse.DiagnosticInfos,
                    acknowledgements,
                    publishResponse.ResponseHeader.StringTable,
                    serverTestServices.Logger);
                Assert.That(publishResponse.SubscriptionId, Is.EqualTo(subscriptionIds[0]));
                Assert.That(publishResponse.NotificationMessage.NotificationData.Count, Is.Zero);
            }

            // Validate ResendData method call returns error from different session contexts

            // call ResendData method from different session context
            resendDataRequestHeader.Timestamp = DateTimeUtc.Now;
            CallResponse callResponse = await m_server.CallAsync(
                resendDataSecurityContext,
                resendDataRequestHeader,
                nodesToCall, RequestLifetime.None).ConfigureAwait(false);

            serverTestServices.SecureChannelContext = m_secureChannelContext;

            Assert.That(callResponse.Results[0].StatusCode, Is.EqualTo(StatusCodes.BadUserAccessDenied));
            ServerFixtureUtils.ValidateResponse(callResponse.ResponseHeader, callResponse.Results, nodesToCall);
            ServerFixtureUtils.ValidateDiagnosticInfos(
                callResponse.DiagnosticInfos,
                nodesToCall,
                callResponse.ResponseHeader.StringTable,
                serverTestServices.Logger);

            // Still nothing to publish since previous ResendData call did not execute
            m_requestHeader.Timestamp = DateTimeUtc.Now;
            publishResponse = await serverTestServices.PublishAsync(
                m_requestHeader,
                acknowledgements).ConfigureAwait(false);

            Assert.That(publishResponse.ResponseHeader.ServiceResult, Is.EqualTo(StatusCodes.Good));
            ServerFixtureUtils.ValidateResponse(publishResponse.ResponseHeader);
            ServerFixtureUtils.ValidateDiagnosticInfos(
                publishResponse.DiagnosticInfos,
                acknowledgements,
                publishResponse.ResponseHeader.StringTable,
                serverTestServices.Logger);
            Assert.That(publishResponse.SubscriptionId, Is.EqualTo(subscriptionIds[0]));
            Assert.That(publishResponse.NotificationMessage.NotificationData.Count, Is.Zero);

            if (updateValues)
            {
                await UpdateValuesAsync(testSet).ConfigureAwait(false);

                // fill queues, but only a single value per resend publish shall be returned
                for (int i = 1; i < queueSize; i++)
                {
                    //If sampling groups are used, samplingInterval needs to be waited before values are queued
                    if (m_fixture.UseSamplingGroupsInReferenceNodeManager)
                    {
                        await Task.Delay((int)(100.0 * 1.7)).ConfigureAwait(false);
                    }
                    await UpdateValuesAsync(testSet).ConfigureAwait(false);
                }

                // Wait a bit to ensure that the server has time to queue the values
                await Task.Delay(1000).ConfigureAwait(false);
            }

            // call ResendData method from the same session context
            await ResendDataCallAsync(StatusCodes.Good, subscriptionIds).ConfigureAwait(false);

            // Data should be available for publishing now
            int totalNotifications = await CollectNotificationsAsync(
                serverTestServices,
                m_requestHeader,
                acknowledgements,
                subscriptionIds[0],
                testSet.Length).ConfigureAwait(false);

            Assert.That(totalNotifications, Is.EqualTo(testSet.Length),
                "One MonitoredItemNotification should be returned for each Node present in the TestSet");

            await Task.Delay(1000).ConfigureAwait(false);

            if (updateValues && queueSize > 1)
            {
                // remaining queue Data should be sent in this publish
                int expectedCount = testSet.Length * ((int)queueSize - 1);
                totalNotifications = await CollectNotificationsAsync(
                    serverTestServices,
                    m_requestHeader,
                    acknowledgements,
                    subscriptionIds[0],
                    expectedCount).ConfigureAwait(false);

                Assert.That(
                    totalNotifications,
                    Is.EqualTo(expectedCount).Within(testSet.Length));
            }

            // Call ResendData method with invalid subscription Id
            await ResendDataCallAsync(StatusCodes.BadSubscriptionIdInvalid, [subscriptionIds[^1] + 20]).ConfigureAwait(false);

            // Nothing to publish since previous ResendData call did not execute
            m_requestHeader.Timestamp = DateTimeUtc.Now;
            publishResponse = await serverTestServices.PublishAsync(
                m_requestHeader,
                acknowledgements).ConfigureAwait(false);

            Assert.That(publishResponse.ResponseHeader.ServiceResult, Is.EqualTo(StatusCodes.Good));
            ServerFixtureUtils.ValidateResponse(publishResponse.ResponseHeader);
            ServerFixtureUtils.ValidateDiagnosticInfos(
                publishResponse.DiagnosticInfos,
                acknowledgements,
                publishResponse.ResponseHeader.StringTable,
                serverTestServices.Logger);
            Assert.That(publishResponse.SubscriptionId, Is.EqualTo(subscriptionIds[0]));
            Assert.That(publishResponse.NotificationMessage.NotificationData.Count, Is.Zero);

            resendDataRequestHeader.Timestamp = DateTimeUtc.Now;
            await m_server.CloseSessionAsync(resendDataSecurityContext, resendDataRequestHeader, true, RequestLifetime.None).ConfigureAwait(false);
        }

        private static async Task<int> CollectNotificationsAsync(
            ServerTestServices serverTestServices,
            RequestHeader requestHeader,
            ArrayOf<SubscriptionAcknowledgement> acknowledgements,
            uint subscriptionId,
            int expectedCount)
        {
            int totalNotifications = 0;
            int retries = 50;
            while (totalNotifications < expectedCount && retries-- > 0)
            {
                requestHeader.Timestamp = DateTime.UtcNow;
                PublishResponse publishResponse = await serverTestServices.PublishAsync(
                    requestHeader,
                    acknowledgements).ConfigureAwait(false);

                Assert.That(publishResponse.ResponseHeader.ServiceResult, Is.EqualTo(StatusCodes.Good));
                ServerFixtureUtils.ValidateResponse(publishResponse.ResponseHeader);
                Assert.That(publishResponse.SubscriptionId, Is.EqualTo(subscriptionId));

                if (publishResponse.NotificationMessage.NotificationData.Count > 0)
                {
                    // acknowledge the notification
                    acknowledgements =
                    [
                        new SubscriptionAcknowledgement
                        {
                            SubscriptionId = subscriptionId,
                            SequenceNumber = publishResponse.NotificationMessage.SequenceNumber
                        }
                    ];

                    foreach (ExtensionObject item in publishResponse.NotificationMessage.NotificationData)
                    {
                        if (item.TryGetValue(out DataChangeNotification? dcn))
                        {
                            totalNotifications += dcn.MonitoredItems.Count;
                        }
                    }
                }

                if (totalNotifications >= expectedCount)
                {
                    break;
                }

                if (!publishResponse.MoreNotifications)
                {
                    // Wait for potential background processing
                    await Task.Delay(100).ConfigureAwait(false);
                }
            }
            return totalNotifications;
        }

        private async Task<ArrayOf<CallMethodRequest>> ResendDataCallAsync(
            StatusCode expectedStatus,
            ArrayOf<uint> subscriptionIds)
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            ILogger logger = telemetry.CreateLogger<ReferenceServerTests>();

            // Find the ResendData method
            ArrayOf<CallMethodRequest> nodesToCall = subscriptionIds
                .ConvertAll(subscriptionId => new CallMethodRequest
                {
                    ObjectId = ObjectIds.Server,
                    MethodId = MethodIds.Server_ResendData,
                    InputArguments = [new Variant(subscriptionId)]
                });

            //call ResendData method with subscription ids
            m_requestHeader.Timestamp = DateTimeUtc.Now;
            CallResponse callResponse = await m_server.CallAsync(
                m_secureChannelContext,
                m_requestHeader,
                nodesToCall, RequestLifetime.None).ConfigureAwait(false);

            Assert.That(callResponse.Results[0].StatusCode, Is.EqualTo(expectedStatus));
            ServerFixtureUtils.ValidateResponse(callResponse.ResponseHeader, callResponse.Results, nodesToCall);
            ServerFixtureUtils.ValidateDiagnosticInfos(
                callResponse.DiagnosticInfos,
                nodesToCall,
                callResponse.ResponseHeader.StringTable,
                logger);

            return nodesToCall;
        }

        /// <summary>
        /// Read Values of NodeIds, determine types, write back new random values.
        /// </summary>
        /// <param name="testSet">The nodeIds to modify.</param>
        private async Task UpdateValuesAsync(NodeId[] testSet)
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            ILogger logger = telemetry.CreateLogger<ReferenceServerTests>();

            // Read values
            RequestHeader requestHeader = m_requestHeader;
            var nodesToRead = testSet
                .Select(nodeId => new ReadValueId
                {
                    NodeId = nodeId,
                    AttributeId = Attributes.Value
                })
                .ToArrayOf();

            ReadResponse readResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                requestHeader,
                kMaxAge,
                TimestampsToReturn.Neither,
                nodesToRead, RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(readResponse.ResponseHeader, readResponse.Results, nodesToRead);
            ServerFixtureUtils.ValidateDiagnosticInfos(
                readResponse.DiagnosticInfos,
                readResponse.Results,
                readResponse.ResponseHeader.StringTable,
                logger);
            Assert.That(readResponse.Results.Count, Is.EqualTo(testSet.Length));

            var modifiedValues = new List<DataValue>();
            foreach (DataValue dataValue in readResponse.Results)
            {
                TypeInfo typeInfo = dataValue.WrappedValue.TypeInfo;
                Assert.That(typeInfo.IsUnknown, Is.False);
                Variant value = m_generator.GetRandomScalar(typeInfo.BuiltInType);
                modifiedValues.Add(new DataValue(value));
            }

            int ii = 0;
            var nodesToWrite = testSet
                .Select(nodeId => new WriteValue
                {
                    NodeId = nodeId,
                    AttributeId = Attributes.Value,
                    Value = modifiedValues[ii++]
                })
                .ToArrayOf();

            // Write Nodes
            requestHeader.Timestamp = DateTimeUtc.Now;
            WriteResponse writeResponse = await m_server.WriteAsync(
                m_secureChannelContext,
                requestHeader,
                nodesToWrite, RequestLifetime.None).ConfigureAwait(false);
            ServerFixtureUtils.ValidateResponse(writeResponse.ResponseHeader, writeResponse.Results, nodesToWrite);
            ServerFixtureUtils.ValidateDiagnosticInfos(
                writeResponse.DiagnosticInfos,
                writeResponse.Results,
                writeResponse.ResponseHeader.StringTable,
                logger);
        }

        /// <summary>
        /// Verifies that an engineering-unit change emits a semantic-change event and a data notification with
        /// SemanticsChanged.
        /// </summary>
        [Test]
        public async Task SemanticChangeNotificationTestAsync()
        {
            var services = new ServerTestServices(m_server, m_secureChannelContext);
            RequestHeader requestHeader = m_requestHeader;
            requestHeader.Timestamp = DateTime.UtcNow;

            // Step 1: Create a subscription
            CreateSubscriptionResponse createSubscriptionResponse = await services.CreateSubscriptionAsync(
                requestHeader,
                100,
                100,
                10,
                0,
                true,
                0).ConfigureAwait(false);

            uint subscriptionId = createSubscriptionResponse.SubscriptionId;

            // We monitor the server EventNotifier for SemanticChangeEventType
            var serverObject = new ReadValueId { NodeId = ObjectIds.Server, AttributeId = Attributes.EventNotifier };
            var eventFilter = new EventFilter();
            eventFilter.AddSelectClause(
                ObjectTypeIds.SemanticChangeEventType,
                QualifiedName.From(BrowseNames.EventId));
            eventFilter.AddSelectClause(
                ObjectTypeIds.SemanticChangeEventType,
                QualifiedName.From(BrowseNames.Changes));

            // Monitor a variable from ReferenceNodeManager (AnalogItem with EngineeringUnits)
            var nodeId = new NodeId("DataAccess_AnalogType_Double",
                (ushort)m_server.CurrentInstance.NamespaceUris.GetIndex(Quickstarts.ReferenceServer.Namespaces.ReferenceServer));

            ArrayOf<MonitoredItemCreateRequest> monitoredItems =
            [
                new MonitoredItemCreateRequest
                {
                    ItemToMonitor = serverObject,
                    MonitoringMode = MonitoringMode.Reporting,
                    RequestedParameters = new MonitoringParameters
                    {
                        ClientHandle = 1,
                        SamplingInterval = 0,
                        QueueSize = 1,
                        DiscardOldest = true,
                        Filter = new ExtensionObject(eventFilter)
                    }
                },
                new MonitoredItemCreateRequest
                {
                    ItemToMonitor = new ReadValueId { NodeId = nodeId, AttributeId = Attributes.Value },
                    MonitoringMode = MonitoringMode.Reporting,
                    RequestedParameters = new MonitoringParameters
                    {
                        ClientHandle = 2,
                        SamplingInterval = 0,
                        QueueSize = 1,
                        DiscardOldest = true
                    }
                }
            ];

            CreateMonitoredItemsResponse createItemsResponse = await services.CreateMonitoredItemsAsync(
                requestHeader,
                subscriptionId,
                TimestampsToReturn.Both,
                monitoredItems).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(createItemsResponse.ResponseHeader, createItemsResponse.Results, monitoredItems);
            Assert.AreEqual(2, createItemsResponse.Results.Count);
            Assert.IsTrue(StatusCode.IsGood(createItemsResponse.Results[0].StatusCode));
            Assert.IsTrue(StatusCode.IsGood(createItemsResponse.Results[1].StatusCode));

            // Initial publish to clear any initial data change notifications
            var acknowledgements = new ArrayOf<SubscriptionAcknowledgement>();
            PublishResponse publishResponse = await services.PublishAsync(requestHeader, acknowledgements).ConfigureAwait(false);

            if (publishResponse.NotificationMessage.NotificationData.Count > 0)
            {
                acknowledgements =
                [
                    new SubscriptionAcknowledgement
                   {
                       SubscriptionId = subscriptionId,
                       SequenceNumber = publishResponse.NotificationMessage.SequenceNumber
                   }
                ];
            }

            // Step 2: Write a new value to a semantic property (EngineeringUnits)
            var euNodeId = new NodeId("DataAccess_AnalogType_DataAccess_AnalogType_Double_EngineeringUnits",
                (ushort)m_server.CurrentInstance.NamespaceUris.GetIndex(Quickstarts.ReferenceServer.Namespaces.ReferenceServer));
            var engUnits = new EUInformation("V", "volt", "http://www.opcfoundation.org/UA/units/un/cefact")
            {
                UnitId = 4274026 // "V"
            };

            ArrayOf<WriteValue> writeValues = new WriteValue[]
            {
                new() {
                    NodeId = euNodeId,
                    AttributeId = Attributes.Value,
                    Value = new DataValue(new ExtensionObject(engUnits))
                }
            }.ToArrayOf();

            requestHeader.Timestamp = DateTime.UtcNow;
            WriteResponse writeResponse = await m_server.WriteAsync(
                m_secureChannelContext,
                requestHeader,
                writeValues, RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(writeResponse.ResponseHeader, writeResponse.Results, writeValues);
            Assert.IsTrue(StatusCode.IsGood(writeResponse.Results[0]));

            // Wait for subscription to deliver the event and data change notification
            await Task.Delay(200).ConfigureAwait(false);

            // Step 3: Issue publish to receive DataChangeNotification and SemanticChangeEvent
            publishResponse = await services.PublishAsync(
                requestHeader,
                acknowledgements).ConfigureAwait(false);

            Assert.IsNotNull(publishResponse.NotificationMessage);
            Assert.IsNotNull(publishResponse.NotificationMessage.NotificationData);
            Assert.IsTrue(publishResponse.NotificationMessage.NotificationData.Count == 2, "One Event and One DataChangeNotification expected.");

            bool dataChangeReceived = false;
            bool semanticsChangedBitSet = false;
            bool eventReceived = false;

            foreach (ExtensionObject data in publishResponse.NotificationMessage.NotificationData)
            {
                if (data.TryGetValue(out DataChangeNotification? dcn))
                {
                    foreach (MonitoredItemNotification item in dcn.MonitoredItems)
                    {
                        if (item.ClientHandle == 2)
                        {
                            dataChangeReceived = true;
                            if (item.Value.StatusCode.SemanticsChanged)
                            {
                                semanticsChangedBitSet = true;
                            }
                        }
                    }
                }
                else if (data.TryGetValue(out EventNotificationList? enl))
                {
                    foreach (EventFieldList e in enl.Events)
                    {
                        if (e.ClientHandle == 1 && e.EventFields.Count >= 2)
                        {
                            bool success = e.EventFields[1]
                                .TryGetStructure(out ArrayOf<SemanticChangeStructureDataType> semanticChangeEvent);

                            if (success && !semanticChangeEvent.IsNull && semanticChangeEvent.Count > 0)
                            {
                                foreach (SemanticChangeStructureDataType change in semanticChangeEvent)
                                {
                                    if (change.Affected == nodeId)
                                    {
                                        eventReceived = true;
                                        break;
                                    }
                                }
                            }
                        }
                    }
                }
            }

            Assert.IsTrue(dataChangeReceived, "Did not receive DataChangeNotification.");
            Assert.IsTrue(semanticsChangedBitSet, "SemanticsChanged bit is not set.");
            Assert.IsTrue(eventReceived, "Did not receive SemanticChangeEvent.");

            // Delete subscription
            await services.DeleteSubscriptionsAsync(
                requestHeader,
                [subscriptionId]).ConfigureAwait(false);
        }

        /// <summary>
        /// Test that historical EventNotifier bits are set on the actual
        /// historical notifier rather than inferred on the Server object.
        /// </summary>
        [Test]
        public async Task HistoricalEventNotifierBitsAreNodeSpecificAsync()
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            ILogger logger = telemetry.CreateLogger<ReferenceServerTests>();

            // Read Server object EventNotifier attribute
            ArrayOf<ReadValueId> readIdCollection =
            [
                new ReadValueId
                {
                    AttributeId = Attributes.EventNotifier,
                    NodeId = ObjectIds.Server
                }
            ];

            m_requestHeader.Timestamp = DateTimeUtc.Now;
            ReadResponse readResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                m_requestHeader,
                0,
                TimestampsToReturn.Both,
                readIdCollection, RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(readResponse.ResponseHeader, readResponse.Results, readIdCollection);
            Assert.That(readResponse.Results.Count, Is.EqualTo(1));
            Assert.That(readResponse.Results[0].WrappedValue.IsNull, Is.False);

            byte eventNotifier = (byte)readResponse.Results[0].WrappedValue;

            // Read history capabilities
            ArrayOf<ReadValueId> historyCapabilitiesReadIds =
            [
                new ReadValueId {
                    AttributeId = Attributes.Value,
                    NodeId = VariableIds.HistoryServerCapabilities_AccessHistoryEventsCapability
                },
                new ReadValueId {
                    AttributeId = Attributes.Value,
                    NodeId = VariableIds.HistoryServerCapabilities_AccessHistoryDataCapability
                }
            ];

            m_requestHeader.Timestamp = DateTimeUtc.Now;
            readResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                m_requestHeader,
                0,
                TimestampsToReturn.Both,
                historyCapabilitiesReadIds, RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(readResponse.ResponseHeader, readResponse.Results, historyCapabilitiesReadIds);
            Assert.That(readResponse.Results.Count, Is.EqualTo(2));

            bool accessHistoryEventsCapability =
                !readResponse.Results[0].WrappedValue.IsNull &&
                (bool)readResponse.Results[0].WrappedValue;
            bool accessHistoryDataCapability =
                !readResponse.Results[1].WrappedValue.IsNull &&
                (bool)readResponse.Results[1].WrappedValue;

            if (logger.IsEnabled(LogLevel.Information))
            {
                logger.LogInformation("Server EventNotifier: {EventNotifier}", eventNotifier);
                logger.LogInformation("AccessHistoryEventsCapability: {AccessHistoryEventsCapability}", accessHistoryEventsCapability);
                logger.LogInformation("AccessHistoryDataCapability: {AccessHistoryDataCapability}", accessHistoryDataCapability);
            }

            Assert.That(
                eventNotifier & EventNotifiers.HistoryRead,
                Is.Zero,
                "The Server object is not itself configured as a historical event notifier.");
            if (accessHistoryEventsCapability)
            {
                ArrayOf<ReadValueId> notifierRead =
                [
                    new ReadValueId
                    {
                        AttributeId = Attributes.EventNotifier,
                        NodeId = new NodeId("CTT", 2)
                    }
                ];
                ReadResponse notifierResponse = await m_server.ReadAsync(
                    m_secureChannelContext,
                    m_requestHeader,
                    0,
                    TimestampsToReturn.Neither,
                    notifierRead,
                    RequestLifetime.None).ConfigureAwait(false);
                Assert.That(
                    (byte)notifierResponse.Results[0].WrappedValue &
                    EventNotifiers.HistoryRead,
                    Is.Not.Zero,
                    "The configured CTT historical event notifier must expose HistoryRead.");
            }

            // Verify SubscribeToEvents bit is set (Server object should always support events)
            Assert.That(eventNotifier & EventNotifiers.SubscribeToEvents,
                Is.Not.Zero,
                "Server EventNotifier should have SubscribeToEvents bit set");
        }

        /// <summary>
        /// Verify that ServerStatus children have matching SourceTimestamp and ServerTimestamp.
        /// </summary>
        [Test]
        public async Task ServerStatusTimestampsMatchAsync()
        {
            ILogger<ReferenceServerTests> logger = m_telemetry.CreateLogger<ReferenceServerTests>();

            // Read ServerStatus children (CurrentTime, StartTime, State, etc.)
            ArrayOf<ReadValueId> nodesToRead =
            [
                new ReadValueId { NodeId = VariableIds.Server_ServerStatus_CurrentTime, AttributeId = Attributes.Value },
                new ReadValueId { NodeId = VariableIds.Server_ServerStatus_StartTime, AttributeId = Attributes.Value },
                new ReadValueId { NodeId = VariableIds.Server_ServerStatus_State, AttributeId = Attributes.Value }
            ];

            m_requestHeader.Timestamp = DateTimeUtc.Now;
            ReadResponse readResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                m_requestHeader,
                0,
                TimestampsToReturn.Both,
                nodesToRead,
                RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(readResponse.ResponseHeader, readResponse.Results, nodesToRead);
            Assert.That(readResponse.Results.Count, Is.EqualTo(3));

            // Verify that SourceTimestamp and ServerTimestamp are equal for all ServerStatus children
            for (int i = 0; i < readResponse.Results.Count; i++)
            {
                DataValue result = readResponse.Results[i];
                if (logger.IsEnabled(LogLevel.Information))
                {
                    logger.LogInformation(
                        "NodeId: {NodeId}, SourceTimestamp: {SourceTimestamp}, ServerTimestamp: {ServerTimestamp}",
                        nodesToRead[i].NodeId,
                        result.SourceTimestamp,
                        result.ServerTimestamp);
                }

                Assert.That(result.ServerTimestamp, Is.EqualTo(result.SourceTimestamp),
                    $"SourceTimestamp and ServerTimestamp should be equal for {nodesToRead[i].NodeId}");
            }
        }

        /// <summary>
        /// Test that the Int32Value node (ns=3;i=2808) allows historical data access.
        /// Verifies the fix for issue #2520 where the node was marked as historizing
        /// but history read operations returned BadHistoryOperationUnsupported.
        /// </summary>
        [Test]
        public async Task HistoryReadInt32ValueNodeAsync()
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            ILogger logger = telemetry.CreateLogger<ReferenceServerTests>();

            // Get the NodeId for Data_Dynamic_Scalar_Int32Value
            var int32ValueNodeId = new NodeId(
                TestData.Variables.Data_Dynamic_Scalar_Int32Value,
                (ushort)m_server.CurrentInstance.NamespaceUris.GetIndex(TestData.Namespaces.TestData));

            if (logger.IsEnabled(LogLevel.Information))
            {
                logger.LogInformation("Testing history read for Int32Value node: {NodeId}", int32ValueNodeId);
            }

            // Verify the node has Historizing attribute set to true
            ArrayOf<ReadValueId> readIdCollection =
            [
                new ReadValueId
                {
                    AttributeId = Attributes.Historizing,
                    NodeId = int32ValueNodeId
                },
                new ReadValueId
                {
                    AttributeId = Attributes.AccessLevel,
                    NodeId = int32ValueNodeId
                }
            ];

            m_requestHeader.Timestamp = DateTimeUtc.Now;
            ReadResponse readResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                m_requestHeader,
                kMaxAge,
                TimestampsToReturn.Neither,
                readIdCollection,
                RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(readResponse.ResponseHeader, readResponse.Results, readIdCollection);
            Assert.That(readResponse.Results.Count, Is.EqualTo(2));

            bool historizing = (bool)readResponse.Results[0].WrappedValue;
            byte accessLevel = (byte)readResponse.Results[1].WrappedValue;

            if (logger.IsEnabled(LogLevel.Information))
            {
                logger.LogInformation("Historizing: {Historizing}, AccessLevel: {AccessLevel}", historizing, accessLevel);
            }

            Assert.That(historizing, Is.True, "Int32Value node should have Historizing=true");
            Assert.That(accessLevel & AccessLevels.HistoryRead,
                Is.Not.Zero,
                "Int32Value node should have HistoryRead access level");

            // Perform a history read operation
            var historyReadDetails = new ReadRawModifiedDetails
            {
                StartTime = DateTimeUtc.Now.SubtractMilliseconds(60 * 60 * 1000),
                EndTime = DateTimeUtc.Now,
                NumValuesPerNode = 10,
                IsReadModified = false,
                ReturnBounds = false
            };

            ArrayOf<HistoryReadValueId> nodesToRead =
            [
                new HistoryReadValueId
                {
                    NodeId = int32ValueNodeId
                }
            ];

            m_requestHeader.Timestamp = DateTimeUtc.Now;
            HistoryReadResponse historyReadResponse = await m_server.HistoryReadAsync(
                m_secureChannelContext,
                m_requestHeader,
                new ExtensionObject(historyReadDetails),
                TimestampsToReturn.Both,
                false,
                nodesToRead,
                RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(historyReadResponse.ResponseHeader, historyReadResponse.Results, nodesToRead);
            Assert.That(historyReadResponse.Results.Count, Is.EqualTo(1));

            HistoryReadResult result = historyReadResponse.Results[0];

            if (logger.IsEnabled(LogLevel.Information))
            {
                logger.LogInformation("History read StatusCode: {StatusCode}", result.StatusCode);
            }

            // The result should be Good or GoodMoreData (if there are more values)
            Assert.That(StatusCode.IsGood(result.StatusCode),
                Is.True,
                $"History read should succeed, but got: {result.StatusCode}");
            Assert.That(result.HistoryData.IsNull, Is.False, "HistoryData should not be null");

            // Verify we got HistoryData back
            if (result.HistoryData.TryGetValue(out HistoryData? historyData))
            {
                if (logger.IsEnabled(LogLevel.Information))
                {
                    logger.LogInformation("Retrieved {Count} history values", historyData.DataValues.Count);
                }
                Assert.That(historyData.DataValues.IsNull, Is.False, "DataValues should not be null");
                Assert.That(historyData.DataValues.Count, Is.GreaterThan(0), "Should have at least one historical value");

                // Verify the data values have proper timestamps
                foreach (DataValue dataValue in historyData.DataValues)
                {
                    Assert.That(dataValue.IsNull, Is.False, "DataValue should not be null");
                    Assert.That(dataValue.ServerTimestamp,
                        Is.Not.EqualTo(DateTimeUtc.MinValue),
                        "DataValue should have a valid ServerTimestamp");
                }
            }
            else
            {
                Assert.Fail("HistoryData body should be of type HistoryData");
            }
        }

        /// <summary>
        /// Test that a HistoryRead on the <c>AccessRights_AccessAll_RO_NotUser</c>
        /// node is denied for the current (anonymous) user. The node advertises
        /// HistoryRead in its AccessLevel but its UserAccessLevel is None, so the
        /// server must return BadUserAccessDenied instead of the historical data.
        /// </summary>
        [Test]
        public async Task HistoryReadUserAccessDeniedNodeAsync()
        {
            ushort namespaceIndex = (ushort)m_server.CurrentInstance.NamespaceUris.GetIndex(
                Quickstarts.ReferenceServer.Namespaces.ReferenceServer);
            var nodeId = new NodeId("AccessRights_AccessAll_RO_NotUser", namespaceIndex);

            // Sanity check: the node advertises HistoryRead in AccessLevel but the
            // current user is not granted HistoryRead via UserAccessLevel.
            ArrayOf<ReadValueId> readIdCollection =
            [
                new ReadValueId
                {
                    AttributeId = Attributes.AccessLevel,
                    NodeId = nodeId
                },
                new ReadValueId
                {
                    AttributeId = Attributes.UserAccessLevel,
                    NodeId = nodeId
                }
            ];

            m_requestHeader.Timestamp = DateTimeUtc.Now;
            ReadResponse readResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                m_requestHeader,
                kMaxAge,
                TimestampsToReturn.Neither,
                readIdCollection,
                RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(readResponse.ResponseHeader, readResponse.Results, readIdCollection);
            Assert.That(readResponse.Results.Count, Is.EqualTo(2));

            byte accessLevel = (byte)readResponse.Results[0].WrappedValue;
            byte userAccessLevel = (byte)readResponse.Results[1].WrappedValue;

            Assert.That(accessLevel & AccessLevels.HistoryRead,
                Is.Not.Zero,
                "Node should advertise HistoryRead in AccessLevel");
            Assert.That(userAccessLevel & AccessLevels.HistoryRead,
                Is.Zero,
                "Node should not grant HistoryRead to the current user via UserAccessLevel");

            // Perform a history read operation; it must be denied for the current user.
            var historyReadDetails = new ReadRawModifiedDetails
            {
                StartTime = DateTimeUtc.Now.SubtractMilliseconds(60 * 60 * 1000),
                EndTime = DateTimeUtc.Now,
                NumValuesPerNode = 10,
                IsReadModified = false,
                ReturnBounds = false
            };

            ArrayOf<HistoryReadValueId> nodesToRead =
            [
                new HistoryReadValueId
                {
                    NodeId = nodeId
                }
            ];

            m_requestHeader.Timestamp = DateTimeUtc.Now;
            HistoryReadResponse historyReadResponse = await m_server.HistoryReadAsync(
                m_secureChannelContext,
                m_requestHeader,
                new ExtensionObject(historyReadDetails),
                TimestampsToReturn.Both,
                false,
                nodesToRead,
                RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(historyReadResponse.ResponseHeader, historyReadResponse.Results, nodesToRead);
            Assert.That(historyReadResponse.Results.Count, Is.EqualTo(1));

            HistoryReadResult result = historyReadResponse.Results[0];

            Assert.That(result.StatusCode.Code,
                Is.EqualTo(StatusCodes.BadUserAccessDenied),
                $"History read on a node without user HistoryRead access should be denied, but got: {result.StatusCode}");
            Assert.That(result.HistoryData.IsNull,
                Is.True,
                "No historical data should be returned when access is denied");
        }

        /// <summary>
        /// Test provisioning mode - server should start with limited namespace.
        /// </summary>
        [Test]
        public async Task ProvisioningModeTestAsync()
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();

            // start Ref server in provisioning mode
            var fixture = new ServerFixture<ReferenceServer>(t => new ReferenceServer(t))
            {
                AllNodeManagers = false,
                OperationLimits = false,
                DurableSubscriptionsEnabled = false,
                AutoAccept = true,
                ProvisioningMode = true
            };

            ReferenceServer server = await fixture.StartAsync().ConfigureAwait(false);

            // Verify provisioning mode is enabled
            Assert.That(server.ProvisioningMode, Is.True, "Server should be in provisioning mode");

            // OPC 10000-12 Annex G.2: the application setup state is reported
            // as ServerState NoConfiguration and through InApplicationSetup.
            Assert.That(server.CurrentInstance.CurrentState, Is.EqualTo(ServerState.NoConfiguration));
            Assert.That(server.CurrentInstance.IsRunning, Is.True, "NoConfiguration still serves requests");
            var configurationManager = (ConfigurationNodeManager)server.CurrentInstance.ConfigurationNodeManager;
            ServerConfigurationState configuration = configurationManager
                .FindPredefinedNode<ServerConfigurationState>(ObjectIds.ServerConfiguration);
            Assert.That(configuration.InApplicationSetup, Is.Not.Null);
            Assert.That(configuration.InApplicationSetup.Value, Is.True);

            // Get endpoints - in provisioning mode, anonymous authentication should not be allowed
            ArrayOf<EndpointDescription> endpoints = server.GetEndpoints();
            Assert.That(endpoints.IsNull, Is.False);
            Assert.That(endpoints.Count, Is.GreaterThan(0), "Server should have endpoints");

            // Check that anonymous token policy is not present for at least one endpoint
            bool hasEndpointWithoutAnonymous = false;
            foreach (EndpointDescription endpoint in endpoints)
            {
                bool hasAnonymous = endpoint.UserIdentityTokens.Contains(
                    policy => policy.TokenType == UserTokenType.Anonymous);
                if (!hasAnonymous)
                {
                    hasEndpointWithoutAnonymous = true;
                    break;
                }
            }
            Assert.That(hasEndpointWithoutAnonymous,
                Is.True,
                "At least one endpoint should not allow anonymous authentication in provisioning mode");

            // Clean up
            await fixture.StopAsync().ConfigureAwait(false);
        }

        /// <summary>
        /// Test that ArrayItemType sub-type nodes are accessible and readable.
        /// </summary>
        [Test]
        public async Task ArrayItemTypeNodesExistAndReadableAsync()
        {
            var nodeIds = new Dictionary<string, NodeId>
            {
                { "YArray", new NodeId("DataAccess_ArrayItemType_YArray", 2) },
                { "XYArray", new NodeId("DataAccess_ArrayItemType_XYArray", 2) },
                { "Image", new NodeId("DataAccess_ArrayItemType_Image", 2) },
                { "Cube", new NodeId("DataAccess_ArrayItemType_Cube", 2) },
                { "NDimension", new NodeId("DataAccess_ArrayItemType_NDimension", 2) }
            };

            foreach (KeyValuePair<string, NodeId> kvp in nodeIds)
            {
                string name = kvp.Key;
                NodeId nodeId = kvp.Value;
                m_requestHeader.Timestamp = DateTimeUtc.Now;
                ArrayOf<ReadValueId> nodesToRead =
                [
                    new ReadValueId { NodeId = nodeId, AttributeId = Attributes.Value },
                    new ReadValueId { NodeId = nodeId, AttributeId = Attributes.DataType },
                    new ReadValueId { NodeId = nodeId, AttributeId = Attributes.ValueRank }
                ];
                ReadResponse readResponse = await m_server.ReadAsync(
                    m_secureChannelContext,
                    m_requestHeader,
                    kMaxAge,
                    TimestampsToReturn.Neither,
                    nodesToRead,
                    RequestLifetime.None).ConfigureAwait(false);

                ServerFixtureUtils.ValidateResponse(readResponse.ResponseHeader, readResponse.Results, nodesToRead);
                Assert.That(readResponse.Results[0].StatusCode, Is.EqualTo(StatusCodes.Good),
                    $"Value read of {name} should succeed");
                Assert.That(readResponse.Results[1].StatusCode, Is.EqualTo(StatusCodes.Good),
                    $"DataType read of {name} should succeed");
                Assert.That(readResponse.Results[2].StatusCode, Is.EqualTo(StatusCodes.Good),
                    $"ValueRank read of {name} should succeed");

                TestContext.Out.WriteLine("{0}: DataType={1}, ValueRank={2}",
                    name,
                    readResponse.Results[1].WrappedValue,
                    readResponse.Results[2].WrappedValue);
            }
        }

        /// <summary>
        /// Test that TriggerNode01 and TriggerNode02 exist, are readable and writable,
        /// and that writing to them fires a BaseEvent.
        /// </summary>
        [Test]
        public async Task TriggerNodesFiringEventsOnWriteAsync()
        {
            var triggerNode01 = new NodeId("NodeIds_Events_TriggerNode01", 2);
            var triggerNode02 = new NodeId("NodeIds_Events_TriggerNode02", 2);
            DateTimeUtc eventWindowStart = DateTime.UtcNow.AddSeconds(-1);

            // Verify both nodes exist and are readable
            foreach (NodeId nodeId in new[] { triggerNode01, triggerNode02 })
            {
                m_requestHeader.Timestamp = DateTimeUtc.Now;
                ArrayOf<ReadValueId> nodesToRead =
                [
                    new ReadValueId { NodeId = nodeId, AttributeId = Attributes.Value }
                ];
                ReadResponse readResponse = await m_server.ReadAsync(
                    m_secureChannelContext,
                    m_requestHeader,
                    kMaxAge,
                    TimestampsToReturn.Neither,
                    nodesToRead,
                    RequestLifetime.None).ConfigureAwait(false);

                ServerFixtureUtils.ValidateResponse(readResponse.ResponseHeader, readResponse.Results, nodesToRead);
                Assert.That(readResponse.Results[0].StatusCode, Is.EqualTo(StatusCodes.Good),
                    $"Read of trigger node {nodeId} should succeed");
            }

            // Verify both nodes are writable
            foreach (NodeId nodeId in new[] { triggerNode01, triggerNode02 })
            {
                m_requestHeader.Timestamp = DateTimeUtc.Now;
                ArrayOf<WriteValue> nodesToWrite =
                [
                    new WriteValue
                    {
                        NodeId = nodeId,
                        AttributeId = Attributes.Value,
                        Value = new DataValue(new Variant(42))
                    }
                ];
                WriteResponse writeResponse = await m_server.WriteAsync(
                    m_secureChannelContext,
                    m_requestHeader,
                    nodesToWrite,
                    RequestLifetime.None).ConfigureAwait(false);

                ServerFixtureUtils.ValidateResponse(writeResponse.ResponseHeader, writeResponse.Results, nodesToWrite);
                Assert.That(writeResponse.Results[0], Is.EqualTo(StatusCodes.Good),
                    $"Write to trigger node {nodeId} should succeed and fire an event");
            }

            var filter = new EventFilter();
            filter.AddSelectClause(
                ObjectTypeIds.BaseEventType,
                BrowseNames.Message,
                Attributes.Value);
            bool captured = false;
            for (int attempt = 0; attempt < 20 && !captured; attempt++)
            {
                m_requestHeader.Timestamp = DateTimeUtc.Now;
                HistoryReadResponse response = await m_server.HistoryReadAsync(
                    m_secureChannelContext,
                    m_requestHeader,
                    new ExtensionObject(new ReadEventDetails
                    {
                        StartTime = eventWindowStart,
                        EndTime = DateTime.UtcNow.AddSeconds(1),
                        NumValuesPerNode = 100,
                        Filter = filter
                    }),
                    TimestampsToReturn.Neither,
                    false,
                    [new HistoryReadValueId { NodeId = new NodeId("CTT", 2) }],
                    RequestLifetime.None).ConfigureAwait(false);
                if (response.Results.Count == 1 &&
                    StatusCode.IsGood(response.Results[0].StatusCode))
                {
                    if (ExtensionObject.ToEncodeable(
                        response.Results[0].HistoryData) is not HistoryEvent historyEvent)
                    {
                        continue;
                    }
                    foreach (HistoryEventFieldList historicalEvent in
                        historyEvent.Events)
                    {
                        if (historicalEvent.EventFields.Count == 1 &&
                            historicalEvent.EventFields[0].TryGetValue(
                                out LocalizedText message) &&
                            message.Text?.Contains(
                                "Trigger event",
                                StringComparison.Ordinal) == true)
                        {
                            captured = true;
                            break;
                        }
                    }
                }
                if (!captured)
                {
                    await Task.Delay(50).ConfigureAwait(false);
                }
            }
            Assert.That(
                captured,
                Is.True,
                "Writing a trigger node must publish and archive the event on the CTT notifier.");
        }

        /// <summary>
        /// Test that the Variant arrays (1D and 2D) are accessible with proper NodeIds.
        /// </summary>
        [Test]
        public async Task VariantArrayNodesExistAndReadableAsync()
        {
            var nodeIds = new Dictionary<string, NodeId>
            {
                { "Scalar_Static_Arrays_Variant", new NodeId("Scalar_Static_Arrays_Variant", 2) },
                { "Scalar_Static_Arrays2D_Variant", new NodeId("Scalar_Static_Arrays2D_Variant", 2) }
            };

            foreach (KeyValuePair<string, NodeId> kvp in nodeIds)
            {
                string name = kvp.Key;
                NodeId nodeId = kvp.Value;
                m_requestHeader.Timestamp = DateTimeUtc.Now;
                ArrayOf<ReadValueId> nodesToRead =
                [
                    new ReadValueId { NodeId = nodeId, AttributeId = Attributes.Value }
                ];
                ReadResponse readResponse = await m_server.ReadAsync(
                    m_secureChannelContext,
                    m_requestHeader,
                    kMaxAge,
                    TimestampsToReturn.Neither,
                    nodesToRead,
                    RequestLifetime.None).ConfigureAwait(false);

                ServerFixtureUtils.ValidateResponse(readResponse.ResponseHeader, readResponse.Results, nodesToRead);
                Assert.That(readResponse.Results[0].StatusCode, Is.EqualTo(StatusCodes.Good),
                    $"Read of {name} should succeed");
            }
        }

        /// <summary>
        /// Verifies that the Variant matrix can be encoded with neighboring results in a batched Read.
        /// </summary>
        [Test]
        public async Task VariantMatrixDoesNotPoisonBatchedReadEncodingAsync()
        {
            ArrayOf<ReadValueId> nodesToRead =
            [
                new ReadValueId
                {
                    NodeId = new NodeId("Scalar_Static_Arrays2D_Int32", 2),
                    AttributeId = Attributes.Value
                },
                new ReadValueId
                {
                    NodeId = new NodeId("Scalar_Static_Arrays2D_Variant", 2),
                    AttributeId = Attributes.Value
                },
                new ReadValueId
                {
                    NodeId = new NodeId("Scalar_Static_Arrays2D_UInt32", 2),
                    AttributeId = Attributes.Value
                }
            ];

            ReadResponse readResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                m_requestHeader,
                kMaxAge,
                TimestampsToReturn.Neither,
                nodesToRead,
                RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(readResponse.ResponseHeader, readResponse.Results, nodesToRead);
            Assert.That(readResponse.Results, Has.Count.EqualTo(nodesToRead.Count));
            for (int i = 0; i < readResponse.Results.Count; i++)
            {
                Assert.That(readResponse.Results[i].StatusCode, Is.EqualTo(StatusCodes.Good));
            }

            using var stream = new MemoryStream();
            using (var encoder = new BinaryEncoder(
                stream,
                m_server.CurrentInstance.MessageContext,
                leaveOpen: true))
            {
                encoder.WriteDataValueArray(null, readResponse.Results);
            }

            stream.Position = 0;
            using var decoder = new BinaryDecoder(stream, m_server.CurrentInstance.MessageContext);
            ArrayOf<DataValue> decodedResults = decoder.ReadDataValueArray(null);

            Assert.That(decodedResults, Has.Count.EqualTo(nodesToRead.Count));
            for (int i = 0; i < decodedResults.Count; i++)
            {
                Assert.That(decodedResults[i].StatusCode, Is.EqualTo(StatusCodes.Good));
                Assert.That(decodedResults[i].WrappedValue, Is.EqualTo(readResponse.Results[i].WrappedValue));
            }
            MatrixOf<Variant> matrix = decodedResults[1].WrappedValue.GetVariantMatrix();
            Assert.That(matrix.Dimensions, Has.Length.EqualTo(2));
            Assert.That(matrix.Dimensions[0], Is.EqualTo(5));
            Assert.That(matrix.Dimensions[1], Is.EqualTo(5));
            Assert.That(matrix.Count, Is.EqualTo(25));
            // CTT multi-dimensional IndexRange tests need scalar elements of a simple type.
            foreach (Variant element in matrix.Span)
            {
                Assert.That(element.TypeInfo.ValueRank, Is.EqualTo(ValueRanks.Scalar));
                Assert.That(element.TypeInfo.BuiltInType, Is.LessThan(BuiltInType.XmlElement));
            }
        }

        /// <summary>
        /// Verifies whole-matrix writes and valid multi-dimensional NumericRange reads and writes.
        /// </summary>
        [Test]
        public async Task MatrixReadWriteAndNumericRangeAsync()
        {
            var nodeId = new NodeId("Scalar_Static_Arrays2D_Int32", 2);
            ArrayOf<ReadValueId> wholeMatrixRead =
            [
                new ReadValueId
                {
                    NodeId = nodeId,
                    AttributeId = Attributes.Value
                }
            ];

            ReadResponse originalRead = await m_server.ReadAsync(
                m_secureChannelContext,
                m_requestHeader,
                kMaxAge,
                TimestampsToReturn.Both,
                wholeMatrixRead,
                RequestLifetime.None).ConfigureAwait(false);
            Assert.That(originalRead.Results[0].StatusCode, Is.EqualTo(StatusCodes.Good));
            Variant originalValue = originalRead.Results[0].WrappedValue;

            try
            {
                MatrixOf<int> matrix = new int[5, 5]
                {
                    { 1, 2, 3, 4, 5 },
                    { 6, 7, 8, 9, 10 },
                    { 11, 12, 13, 14, 15 },
                    { 16, 17, 18, 19, 20 },
                    { 21, 22, 23, 24, 25 }
                };
                ArrayOf<WriteValue> wholeMatrixWrite =
                [
                    new WriteValue
                    {
                        NodeId = nodeId,
                        AttributeId = Attributes.Value,
                        Value = new DataValue(Variant.From(matrix))
                    }
                ];

                WriteResponse wholeWriteResponse = await m_server.WriteAsync(
                    m_secureChannelContext,
                    m_requestHeader,
                    wholeMatrixWrite,
                    RequestLifetime.None).ConfigureAwait(false);
                Assert.That(wholeWriteResponse.Results[0], Is.EqualTo(StatusCodes.Good));

                ArrayOf<ReadValueId> rowRead =
                [
                    new ReadValueId
                    {
                        NodeId = nodeId,
                        AttributeId = Attributes.Value,
                        IndexRange = "1,0:2"
                    }
                ];
                ReadResponse rowReadResponse = await m_server.ReadAsync(
                    m_secureChannelContext,
                    m_requestHeader,
                    kMaxAge,
                    TimestampsToReturn.Both,
                    rowRead,
                    RequestLifetime.None).ConfigureAwait(false);
                DataValue rowValue = rowReadResponse.Results[0];
                Assert.That(rowValue.StatusCode, Is.EqualTo(StatusCodes.Good));
                Assert.That(rowValue.SourceTimestamp.IsNull, Is.False);
                MatrixOf<int> row = rowValue.WrappedValue.GetInt32Matrix();
                Assert.That(row.Dimensions, Has.Length.EqualTo(2));
                Assert.That(row.Dimensions[0], Is.EqualTo(1));
                Assert.That(row.Dimensions[1], Is.EqualTo(3));
                Assert.That(row.Count, Is.EqualTo(3));
                Assert.That(row.Span[0], Is.EqualTo(6));
                Assert.That(row.Span[1], Is.EqualTo(7));
                Assert.That(row.Span[2], Is.EqualTo(8));

                MatrixOf<int> replacement = new int[1, 2] { { 40, 50 } };
                ArrayOf<WriteValue> rangeWrite =
                [
                    new WriteValue
                    {
                        NodeId = nodeId,
                        AttributeId = Attributes.Value,
                        IndexRange = "1,1:2",
                        Value = new DataValue(Variant.From(replacement))
                    }
                ];
                WriteResponse rangeWriteResponse = await m_server.WriteAsync(
                    m_secureChannelContext,
                    m_requestHeader,
                    rangeWrite,
                    RequestLifetime.None).ConfigureAwait(false);
                Assert.That(rangeWriteResponse.Results[0], Is.EqualTo(StatusCodes.Good));

                ReadResponse updatedRowReadResponse = await m_server.ReadAsync(
                    m_secureChannelContext,
                    m_requestHeader,
                    kMaxAge,
                    TimestampsToReturn.Both,
                    rowRead,
                    RequestLifetime.None).ConfigureAwait(false);
                DataValue updatedRowValue = updatedRowReadResponse.Results[0];
                Assert.That(updatedRowValue.StatusCode, Is.EqualTo(StatusCodes.Good));
                MatrixOf<int> updatedRow = updatedRowValue.WrappedValue.GetInt32Matrix();
                Assert.That(updatedRow.Dimensions, Has.Length.EqualTo(2));
                Assert.That(updatedRow.Dimensions[0], Is.EqualTo(1));
                Assert.That(updatedRow.Dimensions[1], Is.EqualTo(3));
                Assert.That(updatedRow.Count, Is.EqualTo(3));
                Assert.That(updatedRow.Span[0], Is.EqualTo(6));
                Assert.That(updatedRow.Span[1], Is.EqualTo(40));
                Assert.That(updatedRow.Span[2], Is.EqualTo(50));
            }
            finally
            {
                ArrayOf<WriteValue> restoreWrite =
                [
                    new WriteValue
                    {
                        NodeId = nodeId,
                        AttributeId = Attributes.Value,
                        Value = new DataValue(originalValue)
                    }
                ];
                WriteResponse restoreResponse = await m_server.WriteAsync(
                    m_secureChannelContext,
                    m_requestHeader,
                    restoreWrite,
                    RequestLifetime.None).ConfigureAwait(false);
                Assert.That(restoreResponse.Results[0], Is.EqualTo(StatusCodes.Good));
            }
        }

        /// <summary>
        /// Test that Enumeration and Image type scalar nodes are accessible.
        /// </summary>
        [Test]
        public async Task ScalarStaticEnumerationAndImageNodesExistAsync()
        {
            var nodeIds = new Dictionary<string, NodeId>
            {
                { "Enumeration", new NodeId("Scalar_Static_Enumeration", 2) },
                { "Image", new NodeId("Scalar_Static_Image", 2) },
                { "ImageBMP", new NodeId("Scalar_Static_ImageBMP", 2) },
                { "ImageGIF", new NodeId("Scalar_Static_ImageGIF", 2) },
                { "ImageJPG", new NodeId("Scalar_Static_ImageJPG", 2) },
                { "ImagePNG", new NodeId("Scalar_Static_ImagePNG", 2) }
            };

            foreach (KeyValuePair<string, NodeId> kvp in nodeIds)
            {
                string name = kvp.Key;
                NodeId nodeId = kvp.Value;
                m_requestHeader.Timestamp = DateTimeUtc.Now;
                ArrayOf<ReadValueId> nodesToRead =
                [
                    new ReadValueId { NodeId = nodeId, AttributeId = Attributes.Value },
                    new ReadValueId { NodeId = nodeId, AttributeId = Attributes.DataType }
                ];
                ReadResponse readResponse = await m_server.ReadAsync(
                    m_secureChannelContext,
                    m_requestHeader,
                    kMaxAge,
                    TimestampsToReturn.Neither,
                    nodesToRead,
                    RequestLifetime.None).ConfigureAwait(false);

                ServerFixtureUtils.ValidateResponse(readResponse.ResponseHeader, readResponse.Results, nodesToRead);
                Assert.That(readResponse.Results[0].StatusCode, Is.EqualTo(StatusCodes.Good),
                    $"Value read of {name} should succeed");
                Assert.That(readResponse.Results[1].StatusCode, Is.EqualTo(StatusCodes.Good),
                    $"DataType read of {name} should succeed");
            }
        }

        /// <summary>
        /// Test that the HasReferenceTypeAndSubType node exists and has the expected references.
        /// </summary>
        [Test]
        public async Task ReferencesHasReferenceTypeAndSubTypePreservesBrowseReferencesAsync()
        {
            int namespaceIndex = m_server.CurrentInstance.NamespaceUris.GetIndex(
                Quickstarts.ReferenceServer.Namespaces.ReferenceServer);
            Assert.That(namespaceIndex, Is.GreaterThan(0));
            var nodeId = new NodeId("References_HasReferenceTypeAndSubType", (ushort)namespaceIndex);
            m_requestHeader.Timestamp = DateTimeUtc.Now;
            ArrayOf<ReadValueId> nodesToRead =
            [
                new ReadValueId { NodeId = nodeId, AttributeId = Attributes.Value }
            ];
            ReadResponse readResponse = await m_server.ReadAsync(
                m_secureChannelContext,
                m_requestHeader,
                kMaxAge,
                TimestampsToReturn.Neither,
                nodesToRead,
                RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(readResponse.ResponseHeader, readResponse.Results, nodesToRead);
            Assert.That(readResponse.Results[0].StatusCode, Is.EqualTo(StatusCodes.Good),
                "Read of References_HasReferenceTypeAndSubType should succeed");

            var instructionsId = new NodeId("Scalar_Instructions", (ushort)namespaceIndex);
            var booleanId = new NodeId("Scalar_Static_Boolean", (ushort)namespaceIndex);
            ArrayOf<BrowseDescription> nodesToBrowse =
            [
                Describe(nodeId, ReferenceTypeIds.HasComponent, BrowseDirection.Forward),
                Describe(nodeId, ReferenceTypeIds.HasComponent, BrowseDirection.Forward, includeSubtypes: true),
                Describe(instructionsId, ReferenceTypeIds.HasComponent, BrowseDirection.Inverse),
                Describe(booleanId, ReferenceTypeIds.HasOrderedComponent, BrowseDirection.Inverse),
                Describe(nodeId, ReferenceTypeIds.References, BrowseDirection.Both, includeSubtypes: true),
                Describe(instructionsId, ReferenceTypeIds.Organizes, BrowseDirection.Inverse),
                Describe(booleanId, ReferenceTypeIds.Organizes, BrowseDirection.Inverse)
            ];
            BrowseResponse response = await m_server.BrowseAsync(
                m_secureChannelContext,
                m_requestHeader,
                null,
                0,
                nodesToBrowse,
                RequestLifetime.None).ConfigureAwait(false);
            ServerFixtureUtils.ValidateResponse(response.ResponseHeader, response.Results, nodesToBrowse);
            for (int index = 0; index < response.Results.Count; index++)
            {
                Assert.That(response.Results[index].StatusCode, Is.EqualTo(StatusCodes.Good));
                Assert.That(response.Results[index].ContinuationPoint.IsEmpty, Is.True);
            }
            Assert.Multiple(() =>
            {
                Assert.That(response.Results[0].References.Count, Is.EqualTo(1));
                Assert.That(response.Results[1].References.Count, Is.EqualTo(2));
                Assert.That(response.Results[2].References.Count, Is.EqualTo(1));
                Assert.That(response.Results[3].References.Count, Is.EqualTo(1));
            });
            ReferenceDescription component = response.Results[0].References[0];
            ReferenceDescription orderedComponent = response.Results[1].References.ToArray()!
                .Single(reference => reference.ReferenceTypeId == ReferenceTypeIds.HasOrderedComponent);
            ReferenceDescription[] allReferences = response.Results[4].References.ToArray()!;
            Assert.Multiple(() =>
            {
                Assert.That(component.ReferenceTypeId, Is.EqualTo(ReferenceTypeIds.HasComponent));
                Assert.That(component.IsForward, Is.True);
                Assert.That(component.NodeId, Is.EqualTo(new ExpandedNodeId(instructionsId)));
                Assert.That(orderedComponent.IsForward, Is.True);
                Assert.That(orderedComponent.NodeId, Is.EqualTo(new ExpandedNodeId(booleanId)));
                Assert.That(response.Results[2].References[0].IsForward, Is.False);
                Assert.That(response.Results[2].References[0].NodeId, Is.EqualTo(new ExpandedNodeId(nodeId)));
                Assert.That(response.Results[3].References[0].IsForward, Is.False);
                Assert.That(response.Results[3].References[0].NodeId, Is.EqualTo(new ExpandedNodeId(nodeId)));
                Assert.That(allReferences, Has.Length.EqualTo(4));
                Assert.That(allReferences!.Any(reference =>
                    reference.ReferenceTypeId == ReferenceTypeIds.HasTypeDefinition &&
                    reference.IsForward &&
                    reference.NodeId == VariableTypeIds.BaseDataVariableType), Is.True);
                Assert.That(allReferences.Any(reference =>
                    reference.ReferenceTypeId == ReferenceTypeIds.Organizes &&
                    !reference.IsForward &&
                    reference.NodeId == new NodeId("References", (ushort)namespaceIndex)), Is.True);
                Assert.That(response.Results[5].References.ToArray()!.Any(reference =>
                    !reference.IsForward &&
                    reference.NodeId == new NodeId("Scalar", (ushort)namespaceIndex)), Is.True);
                Assert.That(response.Results[6].References.ToArray()!.Any(reference =>
                    !reference.IsForward &&
                    reference.NodeId == new NodeId("Scalar_Static", (ushort)namespaceIndex)), Is.True);
            });

            static BrowseDescription Describe(
                NodeId id,
                NodeId referenceTypeId,
                BrowseDirection direction,
                bool includeSubtypes = false)
            {
                return new BrowseDescription
                {
                    NodeId = id,
                    BrowseDirection = direction,
                    ReferenceTypeId = referenceTypeId,
                    IncludeSubtypes = includeSubtypes,
                    ResultMask = (uint)BrowseResultMask.All
                };
            }
        }

        /// <summary>
        /// Verifies that after transferring a subscription to a session that then switches its
        /// identity to one that lacks access to the monitored node, permission caches are
        /// invalidated and subsequent value-change notifications for that node are suppressed.
        /// </summary>
        /// <remarks>
        /// Scenario:
        /// 1. Session A authenticates as user1 (AuthenticatedUser role) and creates a
        ///    subscription monitoring <c>AccessRights_RolePermissions_AuthenticatedUser</c>
        ///    (a node whose RolePermissions allow only the AuthenticatedUser role to read it).
        /// 2. Session B also authenticates as user1 so that TransferSubscriptions accepts the
        ///    transfer (identity check: same username).
        /// 3. The subscription is transferred to session B with sendInitialValues=true; session B
        ///    publishes and receives the initial value — confirming the node is accessible.
        /// 4. Session B re-activates with anonymous identity. This triggers
        ///    <c>SessionActivatedAsync</c> → <c>InvalidatePermissionCacheForSession</c>,
        ///    clearing the cached permission for the transferred item.
        /// 5. Session A (still user1) writes a new value to the restricted node, triggering
        ///    <c>ValidateItemDataChange</c> for session B's item. With the cache cleared, the
        ///    permission is re-evaluated for the anonymous identity → BadUserAccessDenied →
        ///    the notification is suppressed.
        /// 6. Session B publishes: no DataChangeNotification for the restricted node should
        ///    be present, proving that permissions were correctly re-evaluated.
        /// </remarks>
        /// <exception cref="AssertionException">
        /// The fixture has no TCP or HTTPS endpoint, or the selected endpoint has no Username token policy.
        /// </exception>
        [Test]
        public async Task PermissionsRevalidatedAfterTransferSubscriptionsAndReactivationAsync()
        {
            // The ReferenceServer registers its nodes under namespace index 2.
            // "AccessRights_RolePermissions_AuthenticatedUser" allows Browse/Read/Write only
            // for WellKnownRole_AuthenticatedUser; anonymous sessions cannot read it.
            var restrictedNodeId = new NodeId("AccessRights_RolePermissions_AuthenticatedUser", 2);

            EndpointDescription endpoint = m_server.GetEndpoints().Find(e =>
                e.TransportProfileUri is Profiles.UaTcpTransport or Profiles.HttpsBinaryTransport)
                ?? throw new AssertionException("The fixture requires a TCP or HTTPS endpoint.");
            UserTokenPolicy userNamePolicy = endpoint.UserIdentityTokens.Find(
                policy => policy.TokenType == UserTokenType.UserName)
                ?? throw new AssertionException("The endpoint must advertise a Username token policy.");

            var usernameToken = new UserNameIdentityToken
            {
                UserName = "user1",
                Password = System.Text.Encoding.UTF8.GetBytes("password").ToByteString(),
                PolicyId = userNamePolicy.PolicyId
            };

            // Session A: authenticate as user1.
            (RequestHeader headerA, SecureChannelContext channelA) =
                await m_server.CreateAndActivateSessionAsync(
                    "TransferTest_SessionA",
                    useSecurity: false,
                    identityToken: usernameToken).ConfigureAwait(false);
            headerA.Timestamp = DateTimeUtc.Now;

            uint subscriptionId = 0;
            try
            {
                var servicesA = new ServerTestServices(m_server, channelA);

                // Create a subscription in session A.
                CreateSubscriptionResponse subResp = await servicesA.CreateSubscriptionAsync(
                    headerA,
                    requestedPublishingInterval: 100,
                    requestedLifetimeCount: 20,
                    requestedMaxKeepAliveCount: 10,
                    maxNotificationsPerPublish: 0,
                    publishingEnabled: true,
                    priority: 0).ConfigureAwait(false);
                ServerFixtureUtils.ValidateResponse(subResp.ResponseHeader);
                subscriptionId = subResp.SubscriptionId;

                // Monitor the restricted node. Session A (user1 / AuthenticatedUser role)
                // has Read permission, so creation should succeed.
                ArrayOf<MonitoredItemCreateRequest> monitoredItems =
                [
                    new MonitoredItemCreateRequest
                    {
                        ItemToMonitor = new ReadValueId
                        {
                            NodeId = restrictedNodeId,
                            AttributeId = Attributes.Value
                        },
                        MonitoringMode = MonitoringMode.Reporting,
                        RequestedParameters = new MonitoringParameters
                        {
                            ClientHandle = 1,
                            SamplingInterval = -1,
                            QueueSize = 10,
                            DiscardOldest = true
                        }
                    }
                ];

                CreateMonitoredItemsResponse itemsResp = await servicesA.CreateMonitoredItemsAsync(
                    headerA,
                    subscriptionId,
                    TimestampsToReturn.Both,
                    monitoredItems).ConfigureAwait(false);
                ServerFixtureUtils.ValidateResponse(itemsResp.ResponseHeader, itemsResp.Results, monitoredItems);
                Assert.That(StatusCode.IsGood(itemsResp.Results[0].StatusCode), Is.True,
                    "Monitored item creation on restricted node should succeed for AuthenticatedUser.");

                // Write an initial value so the node has a known, non-default value.
                // This also pre-populates the monitored item's last-value cache.
                headerA.Timestamp = DateTimeUtc.Now;
                WriteResponse writeResp0 = await m_server.WriteAsync(
                    channelA,
                    headerA,
                    [new WriteValue
                    {
                        NodeId = restrictedNodeId,
                        AttributeId = Attributes.Value,
                        Value = new DataValue(new Variant((short)10))
                    }],
                    RequestLifetime.None).ConfigureAwait(false);
                ServerFixtureUtils.ValidateResponse(writeResp0.ResponseHeader);
                Assert.That(StatusCode.IsGood(writeResp0.Results[0]), Is.True,
                    "Initial write from user1 should succeed.");

                // Consume any initial notifications queued in session A.
                await Task.Delay(300).ConfigureAwait(false);
                headerA.Timestamp = DateTimeUtc.Now;
                PublishResponse publishA = await servicesA.PublishAsync(headerA, []).ConfigureAwait(false);
                ServerFixtureUtils.ValidateResponse(publishA.ResponseHeader);

                // Session B: authenticate as user1 as well.
                // TransferSubscriptions requires the same username for the identity check to pass.
                (RequestHeader headerB, SecureChannelContext channelB) =
                    await m_server.CreateAndActivateSessionAsync(
                        "TransferTest_SessionB",
                        useSecurity: false,
                        identityToken: usernameToken).ConfigureAwait(false);
                headerB.Timestamp = DateTimeUtc.Now;

                try
                {
                    var servicesB = new ServerTestServices(m_server, channelB);

                    // Transfer the subscription from session A to session B.
                    // sendInitialValues=true causes the server to re-queue the last known value
                    // for all monitored items immediately after transfer.
                    TransferSubscriptionsResponse transferResp =
                        await servicesB.TransferSubscriptionsAsync(
                            headerB,
                            [subscriptionId],
                            sendInitialValues: true).ConfigureAwait(false);
                    ServerFixtureUtils.ValidateResponse(transferResp.ResponseHeader);
                    Assert.That(StatusCode.IsGood(transferResp.Results[0].StatusCode), Is.True,
                        "Subscription transfer should succeed: both sessions use user1 identity.");

                    // Publish from session B to receive the initial-values notification.
                    // At this point session B is still user1 so the read is permitted.
                    await Task.Delay(200).ConfigureAwait(false);
                    headerB.Timestamp = DateTimeUtc.Now;
                    PublishResponse publishB1 = await servicesB.PublishAsync(
                        headerB,
                        publishA.NotificationMessage.SequenceNumber > 0
                            ? [new SubscriptionAcknowledgement
                            {
                                SubscriptionId = subscriptionId,
                                SequenceNumber = publishA.NotificationMessage.SequenceNumber
                            }]
                            : []).ConfigureAwait(false);
                    ServerFixtureUtils.ValidateResponse(publishB1.ResponseHeader);

                    Assert.That(
                        HasDataChangeNotificationForClientHandle(publishB1.NotificationMessage, 1),
                        Is.True,
                        "Session B (user1) must receive the initial data notification for the restricted node.");

                    // Re-activate session B with anonymous identity.
                    // The identity change triggers SessionActivatedAsync →
                    // InvalidatePermissionCacheForSession, clearing the cached permission for
                    // the transferred monitored item.
                    headerB.Timestamp = DateTimeUtc.Now;
                    ActivateSessionResponse reactivateResp = await m_server.ActivateSessionAsync(
                        channelB,
                        headerB,
                        default,
                        [],
                        [],
                        default,
                        null,
                        RequestLifetime.None).ConfigureAwait(false);
                    ServerFixtureUtils.ValidateResponse(reactivateResp.ResponseHeader);

                    // Write a new value from session A (user1 still has Write permission).
                    // This triggers ValidateItemDataChange for session B's monitored item.
                    // With the permission cache cleared, anonymous cannot read the restricted
                    // node → notification is suppressed.
                    headerA.Timestamp = DateTimeUtc.Now;
                    WriteResponse writeResp = await m_server.WriteAsync(
                        channelA,
                        headerA,
                        [new WriteValue
                        {
                            NodeId = restrictedNodeId,
                            AttributeId = Attributes.Value,
                            Value = new DataValue(new Variant((short)99))
                        }],
                        RequestLifetime.None).ConfigureAwait(false);
                    ServerFixtureUtils.ValidateResponse(writeResp.ResponseHeader);
                    Assert.That(StatusCode.IsGood(writeResp.Results[0]), Is.True,
                        "Session A (user1) should still be able to write to the restricted node.");

                    // Allow time for the value change to be processed.
                    await Task.Delay(300).ConfigureAwait(false);

                    // Publish from session B. Because the anonymous identity cannot read the
                    // restricted node, session B must not receive the value; the denied access
                    // is reported as a bad status instead (Part 4 5.13.2.1).
                    headerB.Timestamp = DateTimeUtc.Now;
                    PublishResponse publishB2 = await servicesB.PublishAsync(
                        headerB,
                        [new SubscriptionAcknowledgement
                        {
                            SubscriptionId = subscriptionId,
                            SequenceNumber = publishB1.NotificationMessage.SequenceNumber
                        }]).ConfigureAwait(false);
                    ServerFixtureUtils.ValidateResponse(publishB2.ResponseHeader);

                    foreach (DataValue value in GetDataChangeValuesForClientHandle(
                        publishB2.NotificationMessage, 1))
                    {
                        Assert.That(
                            value.StatusCode == StatusCodes.BadUserAccessDenied ||
                                value.StatusCode == StatusCodes.BadNotReadable,
                            Is.True,
                            "After re-activation as anonymous, session B must only receive an access " +
                            $"error for the AuthenticatedUser-restricted node, got {value.StatusCode}.");
                        Assert.That(value.WrappedValue.IsNull, Is.True,
                            "The restricted value must not be delivered to the anonymous session.");
                    }

                    // Clean up.
                    headerB.Timestamp = DateTimeUtc.Now;
                    await servicesB.DeleteSubscriptionsAsync(headerB, [subscriptionId]).ConfigureAwait(false);
                    subscriptionId = 0;
                }
                finally
                {
                    headerB.Timestamp = DateTimeUtc.Now;
                    await m_server.CloseSessionAsync(
                        channelB,
                        headerB,
                        CancellationToken.None).ConfigureAwait(false);
                }
            }
            finally
            {
                if (subscriptionId != 0)
                {
                    var servicesA = new ServerTestServices(m_server, channelA);
                    headerA.Timestamp = DateTimeUtc.Now;
                    await servicesA.DeleteSubscriptionsAsync(headerA, [subscriptionId])
                        .ConfigureAwait(false);
                }

                headerA.Timestamp = DateTimeUtc.Now;
                await m_server.CloseSessionAsync(
                    channelA,
                    headerA,
                    CancellationToken.None).ConfigureAwait(false);
            }
        }

        /// <summary>
        /// Returns <c>true</c> if any <see cref="DataChangeNotification"/> in the given
        /// <paramref name="message"/> contains a <see cref="MonitoredItemNotification"/>
        /// with the specified <paramref name="clientHandle"/>.
        /// </summary>
        private static bool HasDataChangeNotificationForClientHandle(
            NotificationMessage message,
            uint clientHandle)
        {
            foreach (ExtensionObject extObj in message.NotificationData)
            {
                if (extObj.TryGetValue(out DataChangeNotification? dcn))
                {
                    foreach (MonitoredItemNotification item in dcn.MonitoredItems)
                    {
                        if (item.ClientHandle == clientHandle)
                        {
                            return true;
                        }
                    }
                }
            }

            return false;
        }

        /// <summary>
        /// Returns the values of all <see cref="MonitoredItemNotification"/>s with the specified
        /// <paramref name="clientHandle"/> in the given <paramref name="message"/>.
        /// </summary>
        private static List<DataValue> GetDataChangeValuesForClientHandle(
            NotificationMessage message,
            uint clientHandle)
        {
            var values = new List<DataValue>();
            foreach (ExtensionObject extObj in message.NotificationData)
            {
                if (extObj.TryGetValue(out DataChangeNotification? dcn))
                {
                    foreach (MonitoredItemNotification item in dcn.MonitoredItems)
                    {
                        if (item.ClientHandle == clientHandle)
                        {
                            values.Add(item.Value);
                        }
                    }
                }
            }

            return values;
        }
    }
}