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S7 integration — AbCip/Modbus already have real-simulator integration suites; S7 had zero wire-level coverage despite being a Tier-A driver (all unit tests mocked IS7Client). Picked python-snap7's `snap7.server.Server` over raw Snap7 C library because `pip install` beats per-OS binary-pin maintenance, the package ships a Python __main__ shim that mirrors our existing pymodbus serve.ps1 + *.json pattern structurally, and the python-snap7 project is actively maintained. New project `tests/ZB.MOM.WW.OtOpcUa.Driver.S7.IntegrationTests/` with four moving parts: (a) `Snap7ServerFixture` — collection-scoped TCP probe on `localhost:1102` that sets `SkipReason` when the simulator's not running, matching the `ModbusSimulatorFixture` shape one directory over (same S7_SIM_ENDPOINT env var override convention for pointing at a real S7 CPU on port 102); (b) `PythonSnap7/` — `serve.ps1` wrapper + `server.py` shim + `s7_1500.json` seed profile + `README.md` documenting install / run / known limitations; (c) `S7_1500/S7_1500Profile.cs` — driver-side `S7DriverOptions` whose tag addresses map 1:1 to the JSON profile's seed offsets (DB1.DBW0 u16, DB1.DBW10 i16, DB1.DBD20 i32, DB1.DBD30 f32, DB1.DBX50.3 bool, DB1.DBW100 scratch); (d) `S7_1500SmokeTests` — three tests proving typed reads + write-then-read round-trip work through real S7netplus + real ISO-on-TCP + real snap7 server. Picked port 1102 default instead of S7-standard 102 because 102 is privileged on Linux + triggers Windows Firewall prompt; S7netplus 0.20 has a 5-arg `Plc(CpuType, host, port, rack, slot)` ctor that lets the driver honour `S7DriverOptions.Port`, but the existing driver code called the 4-arg overload + silently hardcoded 102. One-line driver fix (S7Driver.cs:87) threads `_options.Port` through — the S7 unit suite (58/58) still passes unchanged because every unit test uses a fake IS7Client that never sees the real ctor. Server seed-type matrix in `server.py` covers u8 / i8 / u16 / i16 / u32 / i32 / f32 / bool-with-bit / ascii (S7 STRING with max_len header). register_area takes the SrvArea enum value, not the string name — a 15-minute debug after the first test run caught that; documented inline. Per-driver test-fixture coverage docs — eight new files in `docs/drivers/` laying out what each driver's harness actually benchmarks vs. what's trusted from field deployments. Pattern mirrors the AbServer-Test-Fixture.md doc that shipped earlier in this arc: TL;DR → What the fixture is → What it actually covers → What it does NOT cover → When-to-trust table → Follow-up candidates → Key files. Ugly truth the survey made visible: Galaxy + Modbus + (now) S7 + AB CIP have real wire-level coverage; AB Legacy / TwinCAT / FOCAS / OpcUaClient are still contract-only because their libraries ship no fake + no open-source simulator exists (AB Legacy PCCC), no public simulator exists (FOCAS), the vendor SDK has no in-process fake (TwinCAT/ADS.NET), or the test wiring just hasn't happened yet (OpcUaClient could trivially loopback against this repo's own server — flagged as #215). Each doc names the specific follow-up route: Snap7 server for S7 (done), TwinCAT 3 developer-runtime auto-restart for TwinCAT, Tier-C out-of-process Host for FOCAS, lab rigs for AB Legacy + hardware-gated bits of the others. `docs/drivers/README.md` gains a coverage-map section linking all eight. Tracking tasks #215-#222 filed for each PR-able follow-up. Build clean (driver + integration project + docs); S7.Tests 58/58 (unchanged); S7.IntegrationTests 3/3 (new, verified end-to-end against a live python-snap7 server: `driver_reads_seeded_u16_through_real_S7comm`, `driver_reads_seeded_typed_batch`, `driver_write_then_read_round_trip_on_scratch_word`). Next fixture follow-up is #215 (OpcUaClient loopback against own server) — highest ROI of the remaining set, zero external deps. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
114 lines
4.8 KiB
Markdown
114 lines
4.8 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) driven from PowerShell + per-family
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JSON profiles under
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`tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Pymodbus/`.
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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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- **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/Pymodbus/` — simulator
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driver script + per-family JSON profiles
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