Files

Joseph Doherty fdb268cee0 Docs + code-comment sweep — remove stale Pymodbus/ + PythonSnap7/ + LocateBinary references left behind by the native-fallback removal PR. Answer to "is the dev inventory + documentation updated": it was partial; this PR finishes the job.

Files touched — docs/drivers/Modbus-Test-Fixture.md dropped the key-files pointer at deleted Pymodbus/ + flipped "primary launcher is Docker, native fallback retained" framing to "Docker is the only supported launch path" (matching the code). docs/v2/dev-environment.md dropped the "skips both Docker + native-binary paths" parenthetical from AB_SERVER_ENDPOINT + flipped the "Native fallbacks" subsection to a one-liner that says Docker is the only supported path. docs/v2/modbus-test-plan.md rewrote §Harness from "pip install pymodbus + serve.ps1" setup pattern to "docker compose --profile <…> up" + updated the §PR 43 status bullet to point at Docker/profiles/. docs/v2/test-data-sources.md §"CI fixture (task #180)" rewrote the AB CIP section from "LocateBinary() picks binary off PATH" + GitHub Actions zip-download step to "Docker is the only supported reproducible build path" + docker compose GitHub Actions step; dropped the pinned-version SHA256 table + lock-file reference because the Dockerfile's LIBPLCTAG_TAG build-arg is the new pin.

Code docstrings + error messages — these are developer-facing operational text too. ModbusSimulatorFixture SkipReason strings (both branches) now point at `docker compose -f Docker/docker-compose.yml --profile standard up -d` instead of the deleted `Pymodbus\serve.ps1`; doc-comment at the top references Docker/docker-compose.yml. Snap7ServerFixture SkipReason strings + doc-comment point at Docker/docker-compose.yml instead of PythonSnap7/serve.ps1. S7_1500Profile.cs docstring updated. Modbus Dockerfile comment pointing at deleted tests/.../Pymodbus/README.md redirected to docs/drivers/Modbus-Test-Fixture.md. DL205Profile.cs + DL205StringQuirkTests.cs + S7_1500Profile.cs (in Modbus project) docstrings flipped from Pymodbus/*.json references to Docker/profiles/*.json.

Left untouched deliberately: docs/v2/implementation/exit-gate-phase-2-closed.md — that's a historical as-of-2026-04-18 snapshot documenting what was skipped at Phase 2 closure; rewriting would lose the date-stamped context. Its "oitc/modbus-server Docker container not started" + "ab_server binary not on PATH" lines describe the fixture landscape that existed at close time, not current operational guidance.

Final sweep confirms zero remaining `Pymodbus/` / `PythonSnap7/` / `LocateBinary` / `AbServerSeedTag` / `BuildCliArgs` / `AbServerPlcArg` mentions anywhere in tracked files outside that historical exit-gate doc. Whole-solution build still 0 errors.

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

2026-04-20 12:36:19 -04:00

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Modbus test fixture

Coverage map + gap inventory for the Modbus TCP driver's integration-test harness backed by pymodbus simulator profiles per PLC family.

TL;DR: Modbus is the best-covered driver — a real pymodbus server on localhost with per-family seed-register profiles, plus a skip-gate when the simulator port isn't reachable. Covers DL205 / Mitsubishi MELSEC / Siemens S7-1500 family quirks end-to-end. Gaps are mostly error-path + alarm/history shaped (neither is a Modbus-side concept).

What the fixture is

Simulator: pymodbus (Python, BSD) launched as a pinned Docker container at tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Docker/. Docker is the only supported launch path.
Lifecycle: ModbusSimulatorFixture (collection-scoped) TCP-probes localhost:5020 on first use. MODBUS_SIM_ENDPOINT env var overrides the endpoint so the same suite can target a real PLC.
Profiles: DL205Profile, MitsubishiProfile, S7_1500Profile — each composes device-specific register-format + quirk-seed JSON for pymodbus. Profile JSONs live under Docker/profiles/ and are baked into the image.
Compose services: one per profile (standard / dl205 / mitsubishi / s7_1500); only one binds :5020 at a time.
Tests skip via Assert.Skip(sim.SkipReason) when the probe fails; no custom FactAttribute needed because ModbusSimulatorCollection carries the skip reason.

What it actually covers

DL205 (Automation Direct)

DL205SmokeTests — FC16 write → FC03 read round-trip on holding register
DL205CoilMappingTests — Y-output / C-relay / X-input address mapping (octal → Modbus offset)
DL205ExceptionCodeTests — Modbus exception → OPC UA StatusCode mapping
DL205FloatCdabQuirkTests — CDAB word-swap float encoding
DL205StringQuirkTests — packed-string V-memory layout
DL205VMemoryQuirkTests — V-memory octal addressing
DL205XInputTests — X-register read-only enforcement

Mitsubishi MELSEC

MitsubishiSmokeTests — read + write round-trip
MitsubishiQuirkTests — word-order, device-code mapping (D/M/X/Y ranges)

Siemens S7-1500 (Modbus gateway flavor)

S7_1500SmokeTests — read + write round-trip
S7_ByteOrderTests — ABCD/DCBA/BADC/CDAB byte-order matrix

Capability surfaces hit

IReadable + IWritable — full round-trip
ISubscribable — via the shared PollGroupEngine (polled subscription)
IHostConnectivityProbe — TCP-reach transitions

What it does NOT cover

1. No `ITagDiscovery`

Modbus has no symbol table — the driver requires a static tag map from DriverConfig. There is no discovery path to test + none in the fixture.

2. Error-path fuzzing

pymodbus serves the seeded values happily; the fixture can't easily inject exception responses (code 0x01–0x0B) or malformed PDUs. The AbCipStatusMapper-equivalent for exception codes is unit-tested via DL205ExceptionCodeTests but the simulator itself never refuses a read.

3. Variant-specific quirks beyond the three profiles

FX5U / QJ71MT91 Mitsubishi variants — profile scaffolds exist, no tests yet
Non-S7-1500 Siemens (S7-1200 / ET200SP) — byte-order covered but connection-pool + fragmentation quirks untested
DL205-family cousins (DL06, DL260) — no dedicated profile

4. Subscription stress

PollGroupEngine is unit-tested standalone but the simulator doesn't exercise it under multi-register packing stress (FC03 with 125-register batches, boundary splits, etc.).

5. Alarms / history

Not a Modbus concept. Driver doesn't implement IAlarmSource or IHistoryProvider; no test coverage is the correct shape.

When to trust the Modbus fixture, when to reach for a rig

Question	Fixture	Unit tests	Real PLC
"Does FC03/FC06/FC16 work end-to-end?"	yes	-	yes
"Does DL205 octal addressing map correctly?"	yes	yes	yes
"Does float CDAB word-swap round-trip?"	yes	yes	yes
"Does the driver handle exception responses?"	no	yes	yes (required)
"Does packing 125 regs into one FC03 work?"	no	no	yes (required)
"Does FX5U behave like Q-series?"	no	no	yes (required)

Follow-up candidates

Add MODBUS_SIM_ENDPOINT override documentation to docs/v2/test-data-sources.md so operators can point the suite at a lab rig.
Extend pymodbus profiles to inject exception responses — a JSON flag per register saying "next read returns exception 0x04."
Add an FX5U profile once a lab rig is available; the scaffolding is in place.

Key fixture / config files

tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/ModbusSimulatorFixture.cs
tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/DL205/DL205Profile.cs
tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Mitsubishi/MitsubishiProfile.cs
tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/S7/S7_1500Profile.cs
tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Docker/ — Dockerfile + compose + per-family JSON profiles

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