docs: backfill XML documentation across 756 files

Adds <summary>, <param>, <typeparam>, and <inheritdoc/> tags to public
members surfaced by commentchecker — resolves 5,847 of 5,869 issues
(99.6%) across three /fixdocs passes.

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientAlarmTests.cs

@@ -7,6 +7,9 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
 [Trait("Category", "Unit")]
 public sealed class OpcUaClientAlarmTests
 {
+    /// <summary>Verifies that MapSeverity buckets per OPC UA Part 9 guidance.</summary>
+    /// <param name="opcSev">The OPC UA severity value (1–1000).</param>
+    /// <param name="expected">The expected mapped alarm severity.</param>
     [Theory]
     [InlineData((ushort)1, AlarmSeverity.Low)]
     [InlineData((ushort)200, AlarmSeverity.Low)]
@@ -21,6 +24,7 @@ public sealed class OpcUaClientAlarmTests
         OpcUaClientDriver.MapSeverity(opcSev).ShouldBe(expected);
     }
 
+    /// <summary>Verifies that MapSeverity zero maps to Low.</summary>
     [Fact]
     public void MapSeverity_zero_maps_to_Low()
     {
@@ -28,6 +32,7 @@ public sealed class OpcUaClientAlarmTests
         OpcUaClientDriver.MapSeverity(0).ShouldBe(AlarmSeverity.Low);
     }
 
+    /// <summary>Verifies that SubscribeAlarmsAsync without initialize throws InvalidOperationException.</summary>
     [Fact]
     public async Task SubscribeAlarmsAsync_without_initialize_throws_InvalidOperationException()
     {
@@ -36,6 +41,7 @@ public sealed class OpcUaClientAlarmTests
             await drv.SubscribeAlarmsAsync([], TestContext.Current.CancellationToken));
     }
 
+    /// <summary>Verifies that UnsubscribeAlarmsAsync with unknown handle is noop.</summary>
     [Fact]
     public async Task UnsubscribeAlarmsAsync_with_unknown_handle_is_noop()
     {
@@ -44,6 +50,7 @@ public sealed class OpcUaClientAlarmTests
         await drv.UnsubscribeAlarmsAsync(new FakeAlarmHandle(), TestContext.Current.CancellationToken);
     }
 
+    /// <summary>Verifies that AcknowledgeAsync without initialize throws InvalidOperationException.</summary>
     [Fact]
     public async Task AcknowledgeAsync_without_initialize_throws_InvalidOperationException()
     {
@@ -54,6 +61,7 @@ public sealed class OpcUaClientAlarmTests
                 TestContext.Current.CancellationToken));
     }
 
+    /// <summary>Verifies that AcknowledgeAsync with empty batch is noop even without init.</summary>
     [Fact]
     public async Task AcknowledgeAsync_with_empty_batch_is_noop_even_without_init()
     {
@@ -65,6 +73,7 @@ public sealed class OpcUaClientAlarmTests
 
     private sealed class FakeAlarmHandle : IAlarmSubscriptionHandle
     {
+        /// <summary>Gets the diagnostic identifier for this alarm handle.</summary>
         public string DiagnosticId => "fake-alarm";
     }
 }

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientAttributeMappingTests.cs

@@ -8,6 +8,9 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
 [Trait("Category", "Unit")]
 public sealed class OpcUaClientAttributeMappingTests
 {
+    /// <summary>Verifies that MapUpstreamDataType recognizes standard builtin OPC UA types.</summary>
+    /// <param name="typeId">The OPC UA data type ID.</param>
+    /// <param name="expected">The expected driver data type.</param>
     [Theory]
     [InlineData((uint)DataTypes.Boolean, DriverDataType.Boolean)]
     [InlineData((uint)DataTypes.SByte, DriverDataType.Int16)]
@@ -28,6 +31,7 @@ public sealed class OpcUaClientAttributeMappingTests
         OpcUaClientDriver.MapUpstreamDataType(nodeId).ShouldBe(expected);
     }
 
+    /// <summary>Verifies that MapUpstreamDataType maps SByte to Int16 since DriverDataType lacks 8-bit signed.</summary>
     [Fact]
     public void MapUpstreamDataType_maps_SByte_to_Int16_since_DriverDataType_lacks_8bit_signed()
     {
@@ -35,6 +39,7 @@ public sealed class OpcUaClientAttributeMappingTests
         OpcUaClientDriver.MapUpstreamDataType(new NodeId((uint)DataTypes.SByte)).ShouldBe(DriverDataType.Int16);
     }
 
+    /// <summary>Verifies that MapUpstreamDataType maps Byte to UInt16 not Int16.</summary>
     [Fact]
     public void MapUpstreamDataType_maps_Byte_to_UInt16_not_Int16()
     {
@@ -44,6 +49,7 @@ public sealed class OpcUaClientAttributeMappingTests
         OpcUaClientDriver.MapUpstreamDataType(new NodeId((uint)DataTypes.Byte)).ShouldBe(DriverDataType.UInt16);
     }
 
+    /// <summary>Verifies that MapUpstreamDataType falls back to String for unknown custom types.</summary>
     [Fact]
     public void MapUpstreamDataType_falls_back_to_String_for_unknown_custom_types()
     {
@@ -51,12 +57,16 @@ public sealed class OpcUaClientAttributeMappingTests
         OpcUaClientDriver.MapUpstreamDataType(new NodeId("CustomStruct", 2)).ShouldBe(DriverDataType.String);
     }
 
+    /// <summary>Verifies that MapUpstreamDataType handles UtcTime as DateTime.</summary>
     [Fact]
     public void MapUpstreamDataType_handles_UtcTime_as_DateTime()
     {
         OpcUaClientDriver.MapUpstreamDataType(new NodeId((uint)DataTypes.UtcTime)).ShouldBe(DriverDataType.DateTime);
     }
 
+    /// <summary>Verifies that MapAccessLevelToSecurityClass respects the CurrentWrite bit.</summary>
+    /// <param name="accessLevel">The access level byte.</param>
+    /// <param name="expected">The expected security classification.</param>
     [Theory]
     [InlineData((byte)0, SecurityClassification.ViewOnly)]           // no access flags set
     [InlineData((byte)1, SecurityClassification.ViewOnly)]           // CurrentRead only

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientCertAuthTests.cs

@@ -8,6 +8,9 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
 [Trait("Category", "Unit")]
 public sealed class OpcUaClientCertAuthTests
 {
+    /// <summary>
+    /// Verifies that BuildCertificateIdentity rejects missing certificate path.
+    /// </summary>
     [Fact]
     public void BuildCertificateIdentity_rejects_missing_path()
     {
@@ -16,6 +19,9 @@ public sealed class OpcUaClientCertAuthTests
             .Message.ShouldContain("UserCertificatePath");
     }
 
+    /// <summary>
+    /// Verifies that BuildCertificateIdentity rejects nonexistent certificate file.
+    /// </summary>
     [Fact]
     public void BuildCertificateIdentity_rejects_nonexistent_file()
     {
@@ -27,6 +33,9 @@ public sealed class OpcUaClientCertAuthTests
         Should.Throw<FileNotFoundException>(() => OpcUaClientDriver.BuildCertificateIdentity(opts));
     }
 
+    /// <summary>
+    /// Verifies that BuildCertificateIdentity loads a valid PFX with private key.
+    /// </summary>
     [Fact]
     public void BuildCertificateIdentity_loads_a_valid_PFX_with_private_key()
     {

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientDiscoveryTests.cs

@@ -12,6 +12,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
 [Trait("Category", "Unit")]
 public sealed class OpcUaClientDiscoveryTests
 {
+    /// <summary>Verifies that DiscoverAsync throws InvalidOperationException when not initialized.</summary>
     [Fact]
     public async Task DiscoverAsync_without_initialize_throws_InvalidOperationException()
     {
@@ -21,6 +22,7 @@ public sealed class OpcUaClientDiscoveryTests
             await drv.DiscoverAsync(builder, TestContext.Current.CancellationToken));
     }
 
+    /// <summary>Verifies that DiscoverAsync rejects null builder argument.</summary>
     [Fact]
     public void DiscoverAsync_rejects_null_builder()
     {
@@ -29,6 +31,7 @@ public sealed class OpcUaClientDiscoveryTests
             await drv.DiscoverAsync(null!, TestContext.Current.CancellationToken));
     }
 
+    /// <summary>Verifies that discovery configuration has sensible defaults.</summary>
     [Fact]
     public void Discovery_caps_are_sensible_defaults()
     {
@@ -38,17 +41,41 @@ public sealed class OpcUaClientDiscoveryTests
         opts.BrowseRoot.ShouldBeNull("null = default to ObjectsFolder i=85");
     }
 
+    /// <summary>Test builder that provides no-op implementations for discovery tests.</summary>
     private sealed class NullAddressSpaceBuilder : IAddressSpaceBuilder
     {
+        /// <summary>Returns this builder (no-op).</summary>
+        /// <param name="browseName">The browse name of the folder.</param>
+        /// <param name="displayName">The display name of the folder.</param>
         public IAddressSpaceBuilder Folder(string browseName, string displayName) => this;
+
+        /// <summary>Returns a stub handle.</summary>
+        /// <param name="browseName">The browse name of the variable.</param>
+        /// <param name="displayName">The display name of the variable.</param>
+        /// <param name="attributeInfo">The attribute information for the variable.</param>
         public IVariableHandle Variable(string browseName, string displayName, DriverAttributeInfo attributeInfo)
             => new StubHandle();
+
+        /// <summary>No-op property addition.</summary>
+        /// <param name="browseName">The browse name of the property.</param>
+        /// <param name="dataType">The data type of the property.</param>
+        /// <param name="value">The property value.</param>
         public void AddProperty(string browseName, DriverDataType dataType, object? value) { }
+
+        /// <summary>No-op alarm condition attachment.</summary>
+        /// <param name="sourceVariable">The source variable handle.</param>
+        /// <param name="alarmName">The alarm name.</param>
+        /// <param name="alarmInfo">The alarm attribute information.</param>
         public void AttachAlarmCondition(IVariableHandle sourceVariable, string alarmName, DriverAttributeInfo alarmInfo) { }
 
+        /// <summary>Stub variable handle for testing.</summary>
         private sealed class StubHandle : IVariableHandle
         {
+            /// <summary>Gets the full reference as "stub".</summary>
             public string FullReference => "stub";
+
+            /// <summary>Throws NotSupportedException.</summary>
+            /// <param name="info">The alarm condition information (unused).</param>
             public IAlarmConditionSink MarkAsAlarmCondition(AlarmConditionInfo info) => throw new NotSupportedException();
         }
     }

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientDriverScaffoldTests.cs

@@ -12,6 +12,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
 [Trait("Category", "Unit")]
 public sealed class OpcUaClientDriverScaffoldTests
 {
+    /// <summary>Verifies that default options target the standard OPC UA port with anonymous auth.</summary>
     [Fact]
     public void Default_options_target_standard_opcua_port_and_anonymous_auth()
     {
@@ -23,6 +24,7 @@ public sealed class OpcUaClientDriverScaffoldTests
         opts.AutoAcceptCertificates.ShouldBeFalse("production default must reject untrusted server certs");
     }
 
+    /// <summary>Verifies that default timeouts match driver specification section 8.</summary>
     [Fact]
     public void Default_timeouts_match_driver_specs_section_8()
     {
@@ -32,6 +34,7 @@ public sealed class OpcUaClientDriverScaffoldTests
         opts.ReconnectPeriod.ShouldBe(TimeSpan.FromSeconds(5));
     }
 
+    /// <summary>Verifies that driver reports type and ID before connecting.</summary>
     [Fact]
     public void Driver_reports_type_and_id_before_connect()
     {
@@ -41,6 +44,7 @@ public sealed class OpcUaClientDriverScaffoldTests
         drv.GetHealth().State.ShouldBe(DriverState.Unknown);
     }
 
+    /// <summary>Verifies that Initialize against unreachable endpoint transitions to Faulted and throws.</summary>
     [Fact]
     public async Task Initialize_against_unreachable_endpoint_transitions_to_Faulted_and_throws()
     {
@@ -67,6 +71,7 @@ public sealed class OpcUaClientDriverScaffoldTests
         health.LastError.ShouldNotBeNull();
     }
 
+    /// <summary>Verifies that Reinitialize against unreachable endpoint re-throws the error.</summary>
     [Fact]
     public async Task Reinitialize_against_unreachable_endpoint_re_throws()
     {

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientFailoverTests.cs

@@ -7,6 +7,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
 [Trait("Category", "Unit")]
 public sealed class OpcUaClientFailoverTests
 {
+    /// <summary>Verifies that ResolveEndpointCandidates prefers EndpointUrls when provided.</summary>
     [Fact]
     public void ResolveEndpointCandidates_prefers_EndpointUrls_when_provided()
     {
@@ -21,6 +22,7 @@ public sealed class OpcUaClientFailoverTests
         list[1].ShouldBe("opc.tcp://backup:4841");
     }
 
+    /// <summary>Verifies that ResolveEndpointCandidates falls back to single EndpointUrl when list is empty.</summary>
     [Fact]
     public void ResolveEndpointCandidates_falls_back_to_single_EndpointUrl_when_list_empty()
     {
@@ -30,6 +32,7 @@ public sealed class OpcUaClientFailoverTests
         list[0].ShouldBe("opc.tcp://only:4840");
     }
 
+    /// <summary>Verifies that an empty EndpointUrls list is treated as a fallback to EndpointUrl.</summary>
     [Fact]
     public void ResolveEndpointCandidates_empty_list_treated_as_fallback_to_EndpointUrl()
     {
@@ -43,6 +46,7 @@ public sealed class OpcUaClientFailoverTests
         OpcUaClientDriver.ResolveEndpointCandidates(opts).Count.ShouldBe(1);
     }
 
+    /// <summary>Verifies that HostName uses the first candidate before connection.</summary>
     [Fact]
     public void HostName_uses_first_candidate_before_connect()
     {
@@ -55,6 +59,7 @@ public sealed class OpcUaClientFailoverTests
             "pre-connect the dashboard should show the first candidate URL so operators can link back");
     }
 
+    /// <summary>Verifies that initializing against all unreachable endpoints throws AggregateException listing each.</summary>
     [Fact]
     public async Task Initialize_against_all_unreachable_endpoints_throws_AggregateException_listing_each()
     {

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientHistoryTests.cs

@@ -8,6 +8,8 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
 [Trait("Category", "Unit")]
 public sealed class OpcUaClientHistoryTests
 {
+    /// <summary>Verifies MapAggregateToNodeId returns standard Part 13 aggregate for every enum.</summary>
+    /// <param name="agg">The history aggregate type to test.</param>
     [Theory]
     [InlineData(HistoryAggregateType.Average)]
     [InlineData(HistoryAggregateType.Minimum)]
@@ -22,6 +24,7 @@ public sealed class OpcUaClientHistoryTests
         nodeId.NamespaceIndex.ShouldBe((ushort)0);
     }
 
+    /// <summary>Verifies MapAggregateToNodeId rejects invalid enum values.</summary>
     [Fact]
     public void MapAggregateToNodeId_rejects_invalid_enum_value()
     {
@@ -30,6 +33,7 @@ public sealed class OpcUaClientHistoryTests
             OpcUaClientDriver.MapAggregateToNodeId((HistoryAggregateType)99));
     }
 
+    /// <summary>Verifies ReadRawAsync throws without initialization.</summary>
     [Fact]
     public async Task ReadRawAsync_without_initialize_throws_InvalidOperationException()
     {
@@ -40,6 +44,7 @@ public sealed class OpcUaClientHistoryTests
                 TestContext.Current.CancellationToken));
     }
 
+    /// <summary>Verifies ReadRawAsync with malformed NodeId returns empty result.</summary>
     [Fact]
     public async Task ReadRawAsync_with_malformed_NodeId_returns_empty_result_not_throw()
     {
@@ -52,6 +57,7 @@ public sealed class OpcUaClientHistoryTests
         await Task.CompletedTask;
     }
 
+    /// <summary>Verifies ReadProcessedAsync throws without initialization.</summary>
     [Fact]
     public async Task ReadProcessedAsync_without_initialize_throws_InvalidOperationException()
     {
@@ -63,6 +69,7 @@ public sealed class OpcUaClientHistoryTests
                 TestContext.Current.CancellationToken));
     }
 
+    /// <summary>Verifies ReadAtTimeAsync throws without initialization.</summary>
     [Fact]
     public async Task ReadAtTimeAsync_without_initialize_throws_InvalidOperationException()
     {
@@ -73,6 +80,7 @@ public sealed class OpcUaClientHistoryTests
                 TestContext.Current.CancellationToken));
     }
 
+    /// <summary>Verifies ReadEventsAsync throws NotSupportedException as documented.</summary>
     [Fact]
     public async Task ReadEventsAsync_throws_NotSupportedException_as_documented()
     {

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientLowFindingsRegressionTests.cs

@@ -26,6 +26,7 @@ public sealed class OpcUaClientLowFindingsRegressionTests
     // The decision branches are pure logic; assert them against the SDK constants so a
     // regression rewriting `valueRank >= 0` shows up in CI.
 
+    /// <summary>Verifies that ValueRank constants match the OPC UA Part 3 specification values.</summary>
     [Fact]
     public void ValueRank_constants_have_the_OPCUA_Part3_spec_values()
     {
@@ -39,6 +40,9 @@ public sealed class OpcUaClientLowFindingsRegressionTests
         ValueRanks.OneDimension.ShouldBe(1);
     }
 
+    /// <summary>Verifies that IsArray decision matches the valueRank >= 0 boundary.</summary>
+    /// <param name="valueRank">The OPC UA value rank to test.</param>
+    /// <param name="expectedIsArray">Whether the value rank should be treated as an array.</param>
     [Theory]
     [InlineData(-3, false)] // ScalarOrOneDimension — conservatively treated as scalar
     [InlineData(-2, false)] // Any — conservatively treated as scalar
@@ -69,6 +73,7 @@ public sealed class OpcUaClientLowFindingsRegressionTests
     //       with the *same delegate instance*. Confirm that further notifications do not
     //       invoke the handler.
 
+    /// <summary>Verifies that RemoteSubscription record carries handler delegates for detachment.</summary>
     [Fact]
     public void RemoteSubscription_record_carries_handler_delegates_so_they_can_be_detached()
     {
@@ -95,6 +100,7 @@ public sealed class OpcUaClientLowFindingsRegressionTests
             "so UnsubscribeAsync/ShutdownAsync can detach the Notification delegate before disposing the session.");
     }
 
+    /// <summary>Verifies that RemoteAlarmSubscription record carries handler delegate for detachment.</summary>
     [Fact]
     public void RemoteAlarmSubscription_record_carries_handler_delegate_so_it_can_be_detached()
     {
@@ -114,6 +120,7 @@ public sealed class OpcUaClientLowFindingsRegressionTests
             "disposing the session.");
     }
 
+    /// <summary>Verifies that UnsubscribeAsync with unknown handle does not throw after the fix.</summary>
     [Fact]
     public async Task UnsubscribeAsync_unknown_handle_does_not_throw_after_fix()
     {
@@ -124,6 +131,7 @@ public sealed class OpcUaClientLowFindingsRegressionTests
             await drv.UnsubscribeAsync(new FakeHandle(), TestContext.Current.CancellationToken));
     }
 
+    /// <summary>Verifies that UnsubscribeAlarmsAsync with unknown handle does not throw after the fix.</summary>
     [Fact]
     public async Task UnsubscribeAlarmsAsync_unknown_handle_does_not_throw_after_fix()
     {
@@ -132,13 +140,17 @@ public sealed class OpcUaClientLowFindingsRegressionTests
             await drv.UnsubscribeAlarmsAsync(new FakeAlarmHandle(), TestContext.Current.CancellationToken));
     }
 
+    /// <summary>Fake subscription handle for testing.</summary>
     private sealed class FakeHandle : Core.Abstractions.ISubscriptionHandle
     {
+        /// <summary>Gets the diagnostic identifier for this handle.</summary>
         public string DiagnosticId => "fake-sub";
     }
 
+    /// <summary>Fake alarm subscription handle for testing.</summary>
     private sealed class FakeAlarmHandle : Core.Abstractions.IAlarmSubscriptionHandle
     {
+        /// <summary>Gets the diagnostic identifier for this handle.</summary>
         public string DiagnosticId => "fake-alarm-sub";
     }
 }

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientMediumFindingsRegressionTests.cs

@@ -22,6 +22,7 @@ public sealed class OpcUaClientMediumFindingsRegressionTests
 {
     // ---- Driver.OpcUaClient-009 ----
 
+    /// <summary>Verifies that WriteAsync without session returns BadCommunicationError, not BadTimeout.</summary>
     [Fact]
     public async Task WriteAsync_without_session_returns_BadCommunicationError_not_BadTimeout()
     {
@@ -38,6 +39,7 @@ public sealed class OpcUaClientMediumFindingsRegressionTests
 
     // ---- Driver.OpcUaClient-010 ----
 
+    /// <summary>Verifies that Byte data type maps to UInt16, not Int16.</summary>
     [Fact]
     public void MapUpstreamDataType_Byte_maps_to_UInt16_unsigned_family()
     {
@@ -47,6 +49,7 @@ public sealed class OpcUaClientMediumFindingsRegressionTests
         result.ShouldNotBe(DriverDataType.Int16, "Byte is unsigned; Int16 is signed — wrong family");
     }
 
+    /// <summary>Verifies that SByte data type maps to Int16 signed family.</summary>
     [Fact]
     public void MapUpstreamDataType_SByte_still_maps_to_Int16_signed_family()
     {
@@ -57,6 +60,7 @@ public sealed class OpcUaClientMediumFindingsRegressionTests
 
     // ---- Driver.OpcUaClient-012 ----
 
+    /// <summary>Verifies that AutoAcceptCertificates defaults to false.</summary>
     [Fact]
     public void AutoAcceptCertificates_default_is_false_secure_by_default()
     {
@@ -64,6 +68,7 @@ public sealed class OpcUaClientMediumFindingsRegressionTests
             "production default must reject untrusted server certs to prevent MITM");
     }
 
+    /// <summary>Verifies that InitializeAsync with AutoAccept emits a warning log.</summary>
     [Fact]
     public async Task InitializeAsync_AutoAccept_emits_warning_log()
     {
@@ -93,6 +98,7 @@ public sealed class OpcUaClientMediumFindingsRegressionTests
 
     // ---- Driver.OpcUaClient-013 ----
 
+    /// <summary>Verifies that GetMemoryFootprint returns zero before discovery.</summary>
     [Fact]
     public void GetMemoryFootprint_returns_zero_before_first_discovery()
     {
@@ -101,6 +107,7 @@ public sealed class OpcUaClientMediumFindingsRegressionTests
         drv.GetMemoryFootprint().ShouldBe(0L);
     }
 
+    /// <summary>Verifies that FlushOptionalCachesAsync completes without throwing.</summary>
     [Fact]
     public async Task FlushOptionalCachesAsync_completes_without_throwing()
     {
@@ -110,6 +117,7 @@ public sealed class OpcUaClientMediumFindingsRegressionTests
             await drv.FlushOptionalCachesAsync(TestContext.Current.CancellationToken));
     }
 
+    /// <summary>Verifies that FlushOptionalCachesAsync resets the footprint counter.</summary>
     [Fact]
     public async Task FlushOptionalCachesAsync_resets_footprint_counter()
     {
@@ -125,6 +133,7 @@ public sealed class OpcUaClientMediumFindingsRegressionTests
 
     // ---- Driver.OpcUaClient-015: pure-logic paths ----
 
+    /// <summary>Verifies that MapSeverity thresholds match OPC UA AC Part 9 guidance.</summary>
     [Fact]
     public void MapSeverity_thresholds_match_opcua_ac_part9_guidance()
     {
@@ -139,6 +148,7 @@ public sealed class OpcUaClientMediumFindingsRegressionTests
         OpcUaClientDriver.MapSeverity(1000).ShouldBe(AlarmSeverity.Critical);
     }
 
+    /// <summary>Verifies that driver health starts Unknown and is accessible before init.</summary>
     [Fact]
     public void Driver_health_starts_Unknown_and_is_accessible_before_init()
     {
@@ -151,6 +161,7 @@ public sealed class OpcUaClientMediumFindingsRegressionTests
         h.LastSuccessfulRead.ShouldBeNull();
     }
 
+    /// <summary>Verifies that driver Session is null before init and RequireSession throws.</summary>
     [Fact]
     public void Driver_Session_is_null_before_init_so_RequireSession_throws()
     {
@@ -160,6 +171,7 @@ public sealed class OpcUaClientMediumFindingsRegressionTests
         drv.Session.ShouldBeNull();
     }
 
+    /// <summary>Verifies that GetHostStatuses returns single entry keyed to configured endpoint.</summary>
     [Fact]
     public void GetHostStatuses_returns_single_entry_keyed_to_configured_endpoint()
     {
@@ -177,11 +189,26 @@ public sealed class OpcUaClientMediumFindingsRegressionTests
 
     private sealed class CapturingLogger : ILogger<OpcUaClientDriver>
     {
+        /// <summary>Gets the captured log entries.</summary>
         public List<(LogLevel Level, string Message)> Entries { get; } = [];
 
+        /// <summary>Begins a logical scope.</summary>
+        /// <typeparam name="TState">The type of the state object.</typeparam>
+        /// <param name="state">The state to scope.</param>
+        /// <returns>An IDisposable representing the scope.</returns>
         public IDisposable? BeginScope<TState>(TState state) where TState : notnull => null;
+        /// <summary>Checks if logging is enabled for the specified level.</summary>
+        /// <param name="logLevel">The log level.</param>
+        /// <returns>True if logging is enabled.</returns>
         public bool IsEnabled(LogLevel logLevel) => true;
 
+        /// <summary>Logs a message.</summary>
+        /// <typeparam name="TState">The type of the state object.</typeparam>
+        /// <param name="logLevel">The log level.</param>
+        /// <param name="eventId">The event ID.</param>
+        /// <param name="state">The state.</param>
+        /// <param name="exception">The exception.</param>
+        /// <param name="formatter">The formatter function.</param>
         public void Log<TState>(LogLevel logLevel, EventId eventId, TState state,
             Exception? exception, Func<TState, Exception?, string> formatter)
         {

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientNamespaceTests.cs

@@ -14,6 +14,7 @@ public sealed class OpcUaClientNamespaceTests
 {
     // ---- Driver.OpcUaClient-004: TargetNamespaceKind startup enforcement ----
 
+    /// <summary>Verifies that Equipment namespace kind without mapping table is rejected.</summary>
     [Fact]
     public void ValidateNamespaceKind_Equipment_without_mapping_table_is_rejected()
     {
@@ -24,6 +25,7 @@ public sealed class OpcUaClientNamespaceTests
             .Message.ShouldContain("UnsMappingTable");
     }
 
+    /// <summary>Verifies that Equipment namespace kind with mapping table passes.</summary>
     [Fact]
     public void ValidateNamespaceKind_Equipment_with_mapping_table_passes()
     {
@@ -35,6 +37,7 @@ public sealed class OpcUaClientNamespaceTests
         Should.NotThrow(() => OpcUaClientDriver.ValidateNamespaceKind(opts));
     }
 
+    /// <summary>Verifies that SystemPlatform namespace kind with mapping table is rejected.</summary>
     [Fact]
     public void ValidateNamespaceKind_SystemPlatform_with_mapping_table_is_rejected()
     {
@@ -48,6 +51,7 @@ public sealed class OpcUaClientNamespaceTests
             .Message.ShouldContain("SystemPlatform");
     }
 
+    /// <summary>Verifies that SystemPlatform namespace kind without mapping table passes.</summary>
     [Fact]
     public void ValidateNamespaceKind_SystemPlatform_without_mapping_table_passes()
     {
@@ -55,6 +59,7 @@ public sealed class OpcUaClientNamespaceTests
         Should.NotThrow(() => OpcUaClientDriver.ValidateNamespaceKind(opts));
     }
 
+    /// <summary>Verifies that the default target namespace kind is Equipment.</summary>
     [Fact]
     public void Default_TargetNamespaceKind_is_Equipment()
     {
@@ -64,10 +69,12 @@ public sealed class OpcUaClientNamespaceTests
 
     // ---- Driver.OpcUaClient-004: server-stable NodeId encoding ----
 
+    /// <summary>Verifies that NamespaceMap.FromSession rejects null session.</summary>
     [Fact]
     public void NamespaceMap_FromSession_rejects_null_session() =>
         Should.Throw<ArgumentNullException>(() => NamespaceMap.FromSession(null!));
 
+    /// <summary>Verifies that namespace 0 NodeId keeps compact form.</summary>
     [Fact]
     public void NamespaceMap_namespace0_NodeId_keeps_compact_form()
     {
@@ -79,6 +86,7 @@ public sealed class OpcUaClientNamespaceTests
         map.ToStableReference(coreNode).ShouldNotContain("nsu=");
     }
 
+    /// <summary>Verifies that nonzero namespace NodeId is encoded with URI, not index.</summary>
     [Fact]
     public void NamespaceMap_nonzero_namespace_NodeId_is_encoded_with_uri_not_index()
     {
@@ -92,6 +100,7 @@ public sealed class OpcUaClientNamespaceTests
         stable.ShouldNotStartWith("ns=1");
     }
 
+    /// <summary>Verifies that unknown namespace index falls back to raw form.</summary>
     [Fact]
     public void NamespaceMap_unknown_namespace_index_falls_back_to_raw_form()
     {
@@ -102,6 +111,7 @@ public sealed class OpcUaClientNamespaceTests
         Should.NotThrow(() => map.ToStableReference(node));
     }
 
+    /// <summary>Verifies that namespace index and URI lookups are bidirectional.</summary>
     [Fact]
     public void NamespaceMap_index_and_uri_lookups_are_bidirectional()
     {
@@ -113,6 +123,7 @@ public sealed class OpcUaClientNamespaceTests
         map.UriForIndex(99).ShouldBeNull();
     }
 
+    /// <summary>Verifies that NamespaceMap.TryResolve rejects empty and null input.</summary>
     [Fact]
     public void NamespaceMap_TryResolve_rejects_empty_and_null_input()
     {

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientReadWriteTests.cs

@@ -12,6 +12,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
 [Trait("Category", "Unit")]
 public sealed class OpcUaClientReadWriteTests
 {
+    /// <summary>Verifies that ReadAsync throws InvalidOperationException when not initialized.</summary>
     [Fact]
     public async Task ReadAsync_without_initialize_throws_InvalidOperationException()
     {
@@ -20,6 +21,7 @@ public sealed class OpcUaClientReadWriteTests
             await drv.ReadAsync(["ns=2;s=Demo"], TestContext.Current.CancellationToken));
     }
 
+    /// <summary>Verifies that WriteAsync throws InvalidOperationException when not initialized.</summary>
     [Fact]
     public async Task WriteAsync_without_initialize_throws_InvalidOperationException()
     {

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientReconnectTests.cs

@@ -11,12 +11,14 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
 [Trait("Category", "Unit")]
 public sealed class OpcUaClientReconnectTests
 {
+    /// <summary>Verifies that the default reconnect period matches the driver specification of 5 seconds.</summary>
     [Fact]
     public void Default_ReconnectPeriod_matches_driver_specs_5_seconds()
     {
         new OpcUaClientDriverOptions().ReconnectPeriod.ShouldBe(TimeSpan.FromSeconds(5));
     }
 
+    /// <summary>Verifies that reconnect period can be configured for aggressive or relaxed retries.</summary>
     [Fact]
     public void Options_ReconnectPeriod_is_configurable_for_aggressive_or_relaxed_retry()
     {
@@ -24,6 +26,7 @@ public sealed class OpcUaClientReconnectTests
         opts.ReconnectPeriod.ShouldBe(TimeSpan.FromMilliseconds(500));
     }
 
+    /// <summary>Verifies that the driver starts with no reconnect handler active before initialization.</summary>
     [Fact]
     public void Driver_starts_with_no_reconnect_handler_active_pre_init()
     {

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientSecurityPolicyTests.cs

@@ -7,6 +7,8 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
 [Trait("Category", "Unit")]
 public sealed class OpcUaClientSecurityPolicyTests
 {
+    /// <summary>Verifies that every security policy enum value maps to a known non-empty URI.</summary>
+    /// <param name="policy">The OPC UA security policy to map.</param>
     [Theory]
     [InlineData(OpcUaSecurityPolicy.None)]
     [InlineData(OpcUaSecurityPolicy.Basic128Rsa15)]
@@ -24,6 +26,7 @@ public sealed class OpcUaClientSecurityPolicyTests
             uri.ShouldContain(policy.ToString());
     }
 
+    /// <summary>Verifies that None security policy maps to the SDK None URI.</summary>
     [Fact]
     public void MapSecurityPolicy_None_matches_SDK_None_URI()
     {
@@ -31,6 +34,7 @@ public sealed class OpcUaClientSecurityPolicyTests
             .ShouldBe(SecurityPolicies.None);
     }
 
+    /// <summary>Verifies that Basic256Sha256 policy maps to the SDK URI.</summary>
     [Fact]
     public void MapSecurityPolicy_Basic256Sha256_matches_SDK_URI()
     {
@@ -38,6 +42,7 @@ public sealed class OpcUaClientSecurityPolicyTests
             .ShouldBe(SecurityPolicies.Basic256Sha256);
     }
 
+    /// <summary>Verifies that Aes256_Sha256_RsaPss policy maps to the SDK URI.</summary>
     [Fact]
     public void MapSecurityPolicy_Aes256_Sha256_RsaPss_matches_SDK_URI()
     {
@@ -45,6 +50,7 @@ public sealed class OpcUaClientSecurityPolicyTests
             .ShouldBe(SecurityPolicies.Aes256_Sha256_RsaPss);
     }
 
+    /// <summary>Verifies that every security policy enum value has a mapping.</summary>
     [Fact]
     public void Every_enum_value_has_a_mapping()
     {

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientSubscribeAndProbeTests.cs

@@ -13,6 +13,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
 [Trait("Category", "Unit")]
 public sealed class OpcUaClientSubscribeAndProbeTests
 {
+    /// <summary>Verifies that subscribe without initialization throws InvalidOperationException.</summary>
     [Fact]
     public async Task SubscribeAsync_without_initialize_throws_InvalidOperationException()
     {
@@ -21,6 +22,7 @@ public sealed class OpcUaClientSubscribeAndProbeTests
             await drv.SubscribeAsync(["ns=2;s=Demo"], TimeSpan.FromMilliseconds(100), TestContext.Current.CancellationToken));
     }
 
+    /// <summary>Verifies that unsubscribe with unknown handle is a no-op.</summary>
     [Fact]
     public async Task UnsubscribeAsync_with_unknown_handle_is_noop()
     {
@@ -30,6 +32,7 @@ public sealed class OpcUaClientSubscribeAndProbeTests
         await drv.UnsubscribeAsync(new FakeHandle(), TestContext.Current.CancellationToken);
     }
 
+    /// <summary>Verifies that GetHostStatuses returns endpoint URL row before initialization.</summary>
     [Fact]
     public void GetHostStatuses_returns_endpoint_url_row_pre_init()
     {
@@ -43,8 +46,10 @@ public sealed class OpcUaClientSubscribeAndProbeTests
         rows[0].State.ShouldBe(HostState.Unknown);
     }
 
+    /// <summary>A fake subscription handle for testing.</summary>
     private sealed class FakeHandle : ISubscriptionHandle
     {
+        /// <inheritdoc />
         public string DiagnosticId => "fake";
     }
 }