fdb268cee0
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>
118 lines
5.0 KiB
Markdown
118 lines
5.0 KiB
Markdown
# Modbus test fixture
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Coverage map + gap inventory for the Modbus TCP driver's integration-test
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harness backed by `pymodbus` simulator profiles per PLC family.
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**TL;DR:** Modbus is the best-covered driver — a real `pymodbus` server on
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localhost with per-family seed-register profiles, plus a skip-gate when the
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simulator port isn't reachable. Covers DL205 / Mitsubishi MELSEC / Siemens
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S7-1500 family quirks end-to-end. Gaps are mostly error-path + alarm/history
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shaped (neither is a Modbus-side concept).
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## What the fixture is
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- **Simulator**: `pymodbus` (Python, BSD) launched as a pinned Docker
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container at
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`tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Docker/`.
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Docker is the only supported launch path.
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- **Lifecycle**: `ModbusSimulatorFixture` (collection-scoped) TCP-probes
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`localhost:5020` on first use. `MODBUS_SIM_ENDPOINT` env var overrides the
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endpoint so the same suite can target a real PLC.
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- **Profiles**: `DL205Profile`, `MitsubishiProfile`, `S7_1500Profile` —
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each composes device-specific register-format + quirk-seed JSON for pymodbus.
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Profile JSONs live under `Docker/profiles/` and are baked into the image.
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- **Compose services**: one per profile (`standard` / `dl205` /
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`mitsubishi` / `s7_1500`); only one binds `:5020` at a time.
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- **Tests skip** via `Assert.Skip(sim.SkipReason)` when the probe fails; no
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custom FactAttribute needed because `ModbusSimulatorCollection` carries the
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skip reason.
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## What it actually covers
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### DL205 (Automation Direct)
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- `DL205SmokeTests` — FC16 write → FC03 read round-trip on holding register
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- `DL205CoilMappingTests` — Y-output / C-relay / X-input address mapping
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(octal → Modbus offset)
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- `DL205ExceptionCodeTests` — Modbus exception → OPC UA StatusCode mapping
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- `DL205FloatCdabQuirkTests` — CDAB word-swap float encoding
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- `DL205StringQuirkTests` — packed-string V-memory layout
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- `DL205VMemoryQuirkTests` — V-memory octal addressing
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- `DL205XInputTests` — X-register read-only enforcement
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### Mitsubishi MELSEC
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- `MitsubishiSmokeTests` — read + write round-trip
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- `MitsubishiQuirkTests` — word-order, device-code mapping (D/M/X/Y ranges)
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### Siemens S7-1500 (Modbus gateway flavor)
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- `S7_1500SmokeTests` — read + write round-trip
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- `S7_ByteOrderTests` — ABCD/DCBA/BADC/CDAB byte-order matrix
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### Capability surfaces hit
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- `IReadable` + `IWritable` — full round-trip
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- `ISubscribable` — via the shared `PollGroupEngine` (polled subscription)
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- `IHostConnectivityProbe` — TCP-reach transitions
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## What it does NOT cover
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### 1. No `ITagDiscovery`
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Modbus has no symbol table — the driver requires a static tag map from
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`DriverConfig`. There is no discovery path to test + none in the fixture.
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### 2. Error-path fuzzing
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`pymodbus` serves the seeded values happily; the fixture can't easily inject
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exception responses (code 0x01–0x0B) or malformed PDUs. The
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`AbCipStatusMapper`-equivalent for exception codes is unit-tested via
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`DL205ExceptionCodeTests` but the simulator itself never refuses a read.
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### 3. Variant-specific quirks beyond the three profiles
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- FX5U / QJ71MT91 Mitsubishi variants — profile scaffolds exist, no tests yet
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- Non-S7-1500 Siemens (S7-1200 / ET200SP) — byte-order covered but
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connection-pool + fragmentation quirks untested
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- DL205-family cousins (DL06, DL260) — no dedicated profile
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### 4. Subscription stress
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`PollGroupEngine` is unit-tested standalone but the simulator doesn't exercise
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it under multi-register packing stress (FC03 with 125-register batches,
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boundary splits, etc.).
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### 5. Alarms / history
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Not a Modbus concept. Driver doesn't implement `IAlarmSource` or
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`IHistoryProvider`; no test coverage is the correct shape.
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## When to trust the Modbus fixture, when to reach for a rig
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| Question | Fixture | Unit tests | Real PLC |
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| --- | --- | --- | --- |
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| "Does FC03/FC06/FC16 work end-to-end?" | yes | - | yes |
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| "Does DL205 octal addressing map correctly?" | yes | yes | yes |
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| "Does float CDAB word-swap round-trip?" | yes | yes | yes |
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| "Does the driver handle exception responses?" | no | yes | yes (required) |
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| "Does packing 125 regs into one FC03 work?" | no | no | yes (required) |
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| "Does FX5U behave like Q-series?" | no | no | yes (required) |
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## Follow-up candidates
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1. Add `MODBUS_SIM_ENDPOINT` override documentation to
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`docs/v2/test-data-sources.md` so operators can point the suite at a lab rig.
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2. Extend `pymodbus` profiles to inject exception responses — a JSON flag per
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register saying "next read returns exception 0x04."
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3. Add an FX5U profile once a lab rig is available; the scaffolding is in place.
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## Key fixture / config files
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- `tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/ModbusSimulatorFixture.cs`
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- `tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/DL205/DL205Profile.cs`
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- `tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Mitsubishi/MitsubishiProfile.cs`
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- `tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/S7/S7_1500Profile.cs`
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- `tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Docker/` —
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Dockerfile + compose + per-family JSON profiles
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