AB CIP PR 3 — IReadable implementation against libplctag. Introduces IAbCipTagRuntime + IAbCipTagFactory abstraction matching the Modbus transport-factory pattern (ctor optional arg, default production impl injected) so the driver's read/status-mapping logic is unit-testable without a live PLC or the native libplctag binary. LibplctagTagRuntime is the default wire-backed implementation — wraps libplctag.Tag + translates our AbCipDataType enum into GetInt8/GetUInt8/GetInt16/GetUInt16/GetInt32/GetUInt32/GetInt64/GetUInt64/GetFloat32/GetFloat64/GetString/GetBit calls covering Bool (standalone + BOOL-in-DINT via .N bit selector), SInt/USInt, Int/UInt, DInt/UDInt, LInt/ULInt, Real, LReal, String, Dt (epoch DINT), with Structure deferred to PR 6. MapPlcType bridges our libplctag attribute strings (controllogix, compactlogix, micro800) to libplctag.PlcType enum; CompactLogix rolls under ControlLogix per libplctag's family grouping which matches the wire protocol reality. AbCipDriver now implements IReadable — ReadAsync iterates fullReferences preserving order, looks up each tag definition + its device, lazily materialises the tag runtime via EnsureTagRuntimeAsync on first touch (cached thereafter for the lifetime of the device), catches OperationCanceledException to honor cancellation, maps libplctag non-zero status via AbCipStatusMapper.MapLibplctagStatus, catches any other exception as BadCommunicationError. Health surface moves to Healthy on success + Degraded with the last error message on failure. Initialize-failure path disposes the half-created runtime before rethrowing so no native handles leak. DeviceState gains a Runtimes dict alongside the existing TagHandles collection; DisposeHandles walks both so ShutdownAsync + ReinitializeAsync cleanly destroy every native tag. 12 new unit tests in AbCipDriverReadTests using FakeAbCipTag / FakeAbCipTagFactory (test fake under tests/...AbCip.Tests/FakeAbCipTag.cs) covering unknown reference → BadNodeIdUnknown, unknown device → BadNodeIdUnknown, successful DInt read with correct Good status + captured value, lazy-init on first read with reuse across subsequent reads, non-zero libplctag status mapping via AbCipStatusMapper, exception during read surfacing as BadCommunicationError with health Degraded, batched reads preserving order + per-tag status, health Healthy after success, TagCreateParams composition from device + profile (gateway / port / CIP path / libplctag attribute / tag name wiring), cancellation propagation via OperationCanceledException, ShutdownAsync disposing every runtime, Initialize-failure disposing the aborted runtime. Total AbCip unit tests now 88/88 passing. Integration test project scaffolding — tests/ZB.MOM.WW.OtOpcUa.Driver.AbCip.IntegrationTests with AbServerFixture (IAsyncLifetime that starts ab_server when the binary is on PATH, otherwise marks IsAvailable=false), AbServerFact attribute (Fact-equivalent that skips when ab_server is missing), one smoke test exercising DInt read end-to-end. Project runs cleanly — the single smoke test skips on boxes without ab_server (0 failed, 0 passed, 1 skipped) + runs on boxes with it. Follow-up work captured in comments — ab_server CI fixture (download prebuilt Windows x64 binary as GitHub release asset) + per-family JSON profiles + hand-rolled CIP stub for UDT fidelity ship in the PR 6/9-12 window. Solution file updated. Full solution builds 0 errors across all 28 projects. Modbus + other existing tests untouched.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ZB.MOM.WW.OtOpcUa.Driver.AbCip/IAbCipTagRuntime.cs

@@ -0,0 +1,63 @@
+namespace ZB.MOM.WW.OtOpcUa.Driver.AbCip;
+
+/// <summary>
+///     Thin wire-layer abstraction over a single CIP tag. The driver holds one instance per
+///     <c>(device, tag path)</c> pair; the default implementation delegates to
+///     <see cref="LibplctagTagRuntime"/>. Tests swap in a fake via
+///     <see cref="IAbCipTagFactory"/> so the driver's read / write / status-mapping logic can
+///     be exercised without a running PLC or the native libplctag binary.
+/// </summary>
+public interface IAbCipTagRuntime : IDisposable
+{
+    /// <summary>Create the underlying native tag (equivalent to libplctag's <c>plc_tag_create</c>).</summary>
+    Task InitializeAsync(CancellationToken cancellationToken);
+
+    /// <summary>Issue a read; on completion the local buffer holds the current PLC value.</summary>
+    Task ReadAsync(CancellationToken cancellationToken);
+
+    /// <summary>Flush the local buffer to the PLC.</summary>
+    Task WriteAsync(CancellationToken cancellationToken);
+
+    /// <summary>
+    ///     Raw libplctag status code — mapped to an OPC UA StatusCode via
+    ///     <see cref="AbCipStatusMapper.MapLibplctagStatus"/>. Zero on success, negative on error.
+    /// </summary>
+    int GetStatus();
+
+    /// <summary>
+    ///     Decode the local buffer into a boxed .NET value per the tag's configured type.
+    ///     <paramref name="bitIndex"/> is non-null only for BOOL-within-DINT tags captured in
+    ///     the <c>.N</c> syntax at parse time.
+    /// </summary>
+    object? DecodeValue(AbCipDataType type, int? bitIndex);
+
+    /// <summary>
+    ///     Encode <paramref name="value"/> into the local buffer per the tag's type. Callers
+    ///     pair this with <see cref="WriteAsync"/>.
+    /// </summary>
+    void EncodeValue(AbCipDataType type, int? bitIndex, object? value);
+}
+
+/// <summary>
+///     Factory for per-tag runtime handles. Instantiated once per driver, consumed per
+///     <c>(device, tag path)</c> pair at the first read/write.
+/// </summary>
+public interface IAbCipTagFactory
+{
+    IAbCipTagRuntime Create(AbCipTagCreateParams createParams);
+}
+
+/// <summary>Everything libplctag needs to materialise a tag handle.</summary>
+/// <param name="Gateway">Gateway IP / hostname parsed from <see cref="AbCipHostAddress.Gateway"/>.</param>
+/// <param name="Port">EtherNet/IP TCP port — default 44818.</param>
+/// <param name="CipPath">CIP route path, e.g. <c>1,0</c>. Empty for Micro800.</param>
+/// <param name="LibplctagPlcAttribute">libplctag <c>plc=...</c> attribute, per family profile.</param>
+/// <param name="TagName">Logix symbolic tag name as emitted by <see cref="AbCipTagPath.ToLibplctagName"/>.</param>
+/// <param name="Timeout">libplctag operation timeout (applies to Initialize / Read / Write).</param>
+public sealed record AbCipTagCreateParams(
+    string Gateway,
+    int Port,
+    string CipPath,
+    string LibplctagPlcAttribute,
+    string TagName,
+    TimeSpan Timeout);