Joseph Doherty
897b06016c
STALE-STATUS (OpcPlcFixture.cs:39):
- "What the fixture is": opc.tcp://localhost:50000 → opc.tcp://10.100.0.35:50000
(shared Docker host migrated 2026-04-28; fixture already defaults to 10.100.0.35)
CODE-REALITY (OpcUaClientSmokeTests.cs — 3 integration tests open real Secure Channels):
- "What it does NOT cover" §1 ("No UA Secure Channel is ever opened") was wrong
for the integration suite which does open real channels. Rewritten to scope the
no-Secure-Channel claim to the unit suite and list what the integration suite
still doesn't exercise (non-anonymous security policies, signing/encryption,
chunk assembly, keep-alive).
- "When to trust" table: added Integration (opc-plc) column; noted that real OPC UA
read + subscribe ARE covered by integration tests; write not yet exercised on wire.
NOTE on IRediscoverable: OpcUaClientDriver does NOT implement IRediscoverable
(verified: no reference in src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient/).
Doc makes no such claim — no change needed for that aspect.
INLINE COMPLETENESS:
- "Key fixture / config files": added OpcPlcFixture.cs, OpcUaClientSmokeTests.cs,
and Docker/docker-compose.yml entries with correct endpoints and flags.
- Added explicit note in OpcUaClientDriver.cs entry: implements IAlarmSource +
IHistoryProvider (unique among drivers); does NOT implement IRediscoverable.
STRUCTURAL: no rows in links-report.md for this doc.
VERIFY: check_links.py — 0 rows for OpcUaClient-Test-Fixture.md.
187 lines
9.1 KiB
Markdown
187 lines
9.1 KiB
Markdown
# OPC UA Client test fixture
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Coverage map + gap inventory for the OPC UA Client (gateway / aggregation)
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driver.
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**TL;DR:** Wire-level coverage now exists via
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[opc-plc](https://github.com/Azure-Samples/iot-edge-opc-plc) — Microsoft
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Industrial IoT's OPC UA PLC simulator running in Docker (task #215). Real
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Secure Channel, real Session, real MonitoredItem exchange against an
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independent server implementation. Unit tests still carry the exhaustive
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capability matrix (cert auth / security policies / reconnect / failover /
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attribute mapping). Gaps remaining: upstream-server-specific quirks
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(historian aggregates, typed ConditionType events, SDK-publish-queue edge
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behavior under load) — opc-plc uses the same OPCFoundation stack internally
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so fully-independent-stack coverage needs `open62541/open62541` as a second
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image (follow-up).
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## What the fixture is
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**Integration layer** (task #215):
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`tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.IntegrationTests/` stands up
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`mcr.microsoft.com/iotedge/opc-plc:2.14.10` via `Docker/docker-compose.yml`
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on `opc.tcp://10.100.0.35:50000` (the shared Docker host; override via
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`OPCUA_SIM_ENDPOINT`). `OpcPlcFixture` probes the port at
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collection init + skips tests with a clear message when the container's
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not running (matches the Modbus/pymodbus + S7/python-snap7 skip pattern).
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Docker is the launcher — no PowerShell wrapper needed because opc-plc
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ships pre-containerized. Compose-file flags: `--ut` (unsecured transport
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advertised), `--aa` (auto-accept client certs — opc-plc's cert trust store
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resets on each spin-up), `--alm` (alarm simulation for IAlarmSource
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follow-up coverage), `--pn=50000` (port).
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**Unit layer**:
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`tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/` is still the primary
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coverage. Tests inject fakes through the driver's construction path; the
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OPCFoundation.NetStandard `Session` surface is wrapped behind an interface
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the tests mock.
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## What it actually covers
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### Integration (opc-plc Docker, task #215)
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- `OpcUaClientSmokeTests.Client_connects_and_reads_StepUp_node_through_real_OPC_UA_stack` —
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full Secure Channel + Session + `ns=3;s=StepUp` Read round-trip
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- `OpcUaClientSmokeTests.Client_reads_batch_of_varied_types_from_live_simulator` —
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batch Read of UInt32 / Int32 / Boolean; asserts `bool`-specific Variant
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decoding to catch a common attribute-mapping regression
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- `OpcUaClientSmokeTests.Client_subscribe_receives_StepUp_data_changes_from_live_server` —
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real `MonitoredItem` subscription against `ns=3;s=FastUInt1` (ticks every
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100 ms); asserts `OnDataChange` fires within 3 s of subscribe
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Wire-level surfaces verified: `IDriver` + `IReadable` + `ISubscribable` +
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`IHostConnectivityProbe` (via the Secure Channel exchange).
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### Unit
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The surface is broad because `OpcUaClientDriver` is the richest-capability
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driver in the fleet (it's a gateway for another OPC UA server, so it
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mirrors the full capability matrix):
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- `OpcUaClientDriverScaffoldTests` — `IDriver` lifecycle
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- `OpcUaClientReadWriteTests` — read + write lifecycle
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- `OpcUaClientSubscribeAndProbeTests` — monitored-item subscription + probe
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state transitions
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- `OpcUaClientDiscoveryTests` — `GetEndpoints` + endpoint selection
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- `OpcUaClientAttributeMappingTests` — OPC UA node attribute → driver value
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mapping
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- `OpcUaClientSecurityPolicyTests` — `SignAndEncrypt` / `Sign` / `None`
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policy negotiation contract
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- `OpcUaClientCertAuthTests` — cert store paths, revocation-list config
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- `OpcUaClientReconnectTests` — SDK reconnect hook + `TransferSubscriptions`
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across the disconnect boundary
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- `OpcUaClientFailoverTests` — primary → secondary session fallback per
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driver config
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- `OpcUaClientAlarmTests` — A&E severity bucket (1–1000 → Low / Medium /
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High / Critical), subscribe / unsubscribe / ack contract
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- `OpcUaClientHistoryTests` — historical data read + interpolation contract
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Capability surfaces whose contract is verified: `IDriver`, `ITagDiscovery`,
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`IReadable`, `IWritable`, `ISubscribable`, `IHostConnectivityProbe`,
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`IAlarmSource`, `IHistoryProvider`.
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## What it does NOT cover
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### 1. Full real-stack exchange (unit tests only)
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The **unit** suite mocks `Session.ReadAsync`, `Session.CreateSubscription`,
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`Session.AddItem`, etc. — no UA Secure Channel is opened. The **integration**
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suite (`OpcUaClientSmokeTests`, task #215) does open a real Secure Channel
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against opc-plc and exercises Read + Subscribe end-to-end. What remains
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untested even in the integration suite: certificate validation under
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non-anonymous security policies, signing/encryption, nonce handling, chunk
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assembly, keep-alive cadence — all SDK-internal.
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### 2. Subscription transfer across reconnect
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Contract test: "after a simulated reconnect, `TransferSubscriptions` is
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called with the right handles." Real behavior: SDK re-publishes against the
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new channel and some events can be lost depending on publish-queue state.
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The lossy window is not characterized.
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### 3. Large-scale subscription stress
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100+ monitored items with heterogeneous publish intervals under a single
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session — the shape that breaks publish-queue-size tuning in the wild — is
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not exercised.
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### 4. Real historian mappings
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`IHistoryProvider.ReadRawAsync` + `ReadProcessedAsync` +
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`ReadAtTimeAsync` + `ReadEventsAsync` are contract-mocked. Against a real
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historian (AVEVA Historian, Prosys historian, Kepware LocalHistorian) each
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has specific interpolation + bad-quality-handling quirks the contract test
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doesn't see.
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### 5. Real A&E events
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Alarm subscription is mocked via filtered monitored items; the actual
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`EventFilter` select-clause behavior against a server that exposes typed
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ConditionType events (non-base `BaseEventType`) is not verified.
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### 6. Authentication variants
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- Anonymous, UserName/Password, X509 cert tokens — each is contract-tested
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but not exchanged against a server that actually enforces each.
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- LDAP-backed `UserName` (matching this repo's server-side
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`LdapUserAuthenticator`) requires a live LDAP round-trip; not tested.
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## When to trust OpcUaClient tests, when to reach for a server
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| Question | Unit tests | Integration (opc-plc) | Real upstream server |
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| --- | --- | --- | --- |
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| "Does severity 750 bucket as High?" | yes | - | yes |
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| "Does the driver call `TransferSubscriptions` after reconnect?" | yes | - | yes |
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| "Does a real OPC UA read round-trip work?" | no | yes | yes |
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| "Does a real OPC UA subscribe deliver changes?" | no | yes | yes |
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| "Does write round-trip work against a live server?" | no | no (not yet exercised) | yes (required) |
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| "Does event-filter-based alarm subscription return ConditionType events?" | no | no | yes (required) |
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| "Does history read from AVEVA Historian return correct aggregates?" | no | no | yes (required) |
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| "Does the SDK's publish queue lose notifications under load?" | no | no | yes (stress) |
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## Follow-up candidates
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The easiest win here is to **wire the client driver tests against this
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repo's own server**. The v2 integration test project
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`tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.IntegrationTests/DualEndpointTests.cs`
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(the v2 replacement for the retired v1 `OpcUaServerIntegrationTests`) already
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stands up a real OPC UA server on a non-default port with a seeded
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FakeDriver. An `OpcUaClientLiveLoopbackTests` that connects the client
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driver to that server would give:
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- Real Secure Channel negotiation
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- Real Session / Subscription / MonitoredItem exchange
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- Real read/write round-trip
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- Real certificate validation (the integration test already sets up PKI)
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It wouldn't cover upstream-server-specific quirks (AVEVA Historian, Kepware,
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Prosys), but it would cover 80% of the SDK surface the driver sits on top
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of.
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Beyond that:
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1. **Prosys OPC UA Simulation Server** — free, Windows-available, scriptable.
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2. **UaExpert Server-Side Simulator** — Unified Automation's sample server;
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good coverage of typed ConditionType events.
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3. **Dedicated historian integration lab** — only path for
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historian-specific coverage.
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## Key fixture / config files
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- `tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/` — unit tests with
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mocked `Session`
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- `tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.IntegrationTests/OpcPlcFixture.cs`
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— collection fixture; parses `OPCUA_SIM_ENDPOINT` (default
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`opc.tcp://10.100.0.35:50000`), TCP-probes at collection init, records
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`SkipReason` when unreachable
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- `tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.IntegrationTests/OpcUaClientSmokeTests.cs`
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— wire-level test suite (3 `[Fact]` methods: read, batch read, subscribe)
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- `tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.IntegrationTests/Docker/docker-compose.yml`
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— `mcr.microsoft.com/iotedge/opc-plc:2.14.10` with `--ut --aa --alm --pn=50000`
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- `src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient/OpcUaClientDriver.cs` — ctor +
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session-factory seam tests mock through; implements `IAlarmSource` +
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`IHistoryProvider` (unique among drivers); does NOT implement `IRediscoverable`
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- `tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.IntegrationTests/DualEndpointTests.cs` —
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the v2 dual-endpoint integration harness a future loopback client test could
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piggyback on (v1 `OpcUaServerIntegrationTests.cs` retired with the v1 server project)
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