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Joseph Doherty 0e1dcc119e Remove native-launcher fallbacks for the four Dockerized fixtures — Docker is the only supported path for Modbus / S7 / AB CIP / OpcUaClient integration. Native paths stay in place only where Docker isn't compatible (Galaxy: MXAccess COM + Windows-only; TwinCAT: Beckhoff runtime vs Hyper-V; FOCAS: closed-source Fanuc Fwlib32.dll; AB Legacy: PCCC has no OSS simulator). Simplifies the fixture landscape + removes the "which path do I run" ambiguity; removes two full native-launcher directories + the AB CIP native-spawn path; removes the parallel profile-as-CLI-arg-builder code from AbServerFixture.

Modbus — deletes tests/.../Modbus.IntegrationTests/Pymodbus/ (serve.ps1, standard.json, dl205.json, mitsubishi.json, s7_1500.json, README.md). Profile JSONs live only under Docker/profiles/ now. Docker/README.md loses its "Native-Python fallback" section; docs/drivers/Modbus-Test-Fixture.md "What the fixture is" bullet flipped from "primary launcher is Docker, native fallback under Pymodbus/" to "Docker is the only supported launch path".

S7 — deletes tests/.../S7.IntegrationTests/PythonSnap7/ (server.py, s7_1500.json, serve.ps1, README.md). Docker/README.md loses "Native-Python fallback"; docs/drivers/S7-Test-Fixture.md updated to match.

AB CIP — the biggest simplification because the native-binary spawn had the most code. AbServerFixture.cs rewrites: drops Process management (no more Process _proc + Kill/WaitForExit), drops LocateBinary() PATH lookup, drops the IAsyncLifetime initialize-spawns-server behavior. Fixture is now a thin TCP probe against localhost:44818 (or AB_SERVER_ENDPOINT override) — same shape as Snap7ServerFixture / ModbusSimulatorFixture / OpcPlcFixture. IsServerAvailable() simplifies to a single 500 ms probe. AbServerProfile.cs drops AbServerPlcArg + SeedTags + BuildCliArgs + ToCliSpec + the entire AbServerSeedTag record — the compose file is the canonical source of truth for which tags + which --plc mode each family gets; the profile record now carries just Family + ComposeProfile (matches the docker-compose service key) + Notes. KnownProfiles.ForFamily + .All stay for tests that iterate families. AbServerProfileTests.cs rewrites to match: drops BuildCliArgs_* + ToCliSpec_* + SeedTags_* tests; keeps the family-coverage contract tests + verifies the ComposeProfile strings match compose-file service names (a typo in either surfaces as a unit-test failure, not a silent "wrong family booted" at runtime). Docker/README.md loses "Native-binary fallback" section; docs/drivers/AbServer-Test-Fixture.md "What the fixture is" flipped to Docker-only with clearer skip rules.

dev-environment.md §Docker fixtures — the "Native fallbacks" subsection goes away; replaced with a one-line note that Docker is the only supported path for these four fixtures + a fresh clone needs Docker Desktop and nothing else.

Verified: whole-solution build 0 errors, AB CIP profile unit tests 6/6, AB CIP Docker smoke 4/4 (all family theory rows), S7 Docker smoke 3/3. Container lifecycle clean. The deleted native code surface was already redundant — every fixture the native paths served is now covered by Docker; keeping them invited drift between the two paths (the original AB CIP native profile had three undetected bugs per the #162 commit message: case-sensitive --plc, bracket tag notation, --path=1,0 requirement — noise the Docker path now avoids by never running the buggy code).

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

2026-04-20 12:27:44 -04:00

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Siemens S7 test fixture

Coverage map + gap inventory for the S7 driver.

TL;DR: S7 now has a wire-level integration fixture backed by python-snap7's Server class (task #216). Atomic reads (u16 / i16 / i32 / f32 / bool-with-bit) + DB write-then-read round-trip are exercised end-to-end through S7netplus + real ISO-on-TCP on localhost:1102. Unit tests still carry everything else (address parsing, error-branch handling, probe-loop contract). Gaps remaining are variant-quirk-shaped: Optimized-DB symbolic access, PG/OP session types, PUT/GET-disabled enforcement — all need real hardware.

What the fixture is

Integration layer (task #216): tests/ZB.MOM.WW.OtOpcUa.Driver.S7.IntegrationTests/ stands up a python-snap7 Server via Docker/docker-compose.yml --profile s7_1500 on localhost:1102 (pinned python:3.12-slim-bookworm base + python-snap7>=2.0). Docker is the only supported launch path. Snap7ServerFixture probes the port at collection init + skips with a clear message when unreachable (matches the pymodbus pattern). server.py (baked into the image under Docker/) reads a JSON profile

seeds DB/MB bytes at declared offsets; seeds are typed (u16 / i16 / i32 / f32 / bool / ascii for S7 STRING).

Unit layer: tests/ZB.MOM.WW.OtOpcUa.Driver.S7.Tests/ covers everything the wire-level suite doesn't — address parsing, error branches, probe-loop contract. All tests tagged [Trait("Category", "Unit")].

The driver ctor change that made this possible: Plc(CpuType, host, port, rack, slot) — S7netplus 0.20's 5-arg overload — wires S7DriverOptions.Port through so the simulator can bind 1102 (non-privileged) instead of 102 (root / Firewall-prompt territory).

What it actually covers

Integration (python-snap7, task #216)

S7_1500SmokeTests.Driver_reads_seeded_u16_through_real_S7comm — DB1.DBW0 read via real S7netplus over TCP + simulator; proves handshake + read path
S7_1500SmokeTests.Driver_reads_seeded_typed_batch — i16, i32, f32, bool-with-bit in one batch call; proves typed decode per S7DataType
S7_1500SmokeTests.Driver_write_then_read_round_trip_on_scratch_word — DB1.DBW100 write → read-back; proves write path + buffer visibility

Unit

S7AddressParserTests — S7 address syntax (DB1.DBD0, M10.3, IW4, etc.)
S7DriverScaffoldTests — IDriver lifecycle (init / reinit / shutdown / health)
S7DriverReadWriteTests — error paths (uninitialized read/write, bad addresses, transport exceptions)
S7DiscoveryAndSubscribeTests — ITagDiscovery.DiscoverAsync + polled ISubscribable contract with the shared PollGroupEngine

Capability surfaces whose contract is verified: IDriver, ITagDiscovery, IReadable, IWritable, ISubscribable, IHostConnectivityProbe. Wire-level surfaces verified: IReadable, IWritable.

What it does NOT cover

1. Wire-level anything

No ISO-on-TCP frame is ever sent during the test suite. S7netplus is the only wire-path abstraction and it has no in-process fake mode; the shipping choice was to contract-test via IS7Client rather than patch into S7netplus internals.

2. Read/write happy path

Every S7DriverReadWriteTests case exercises error branches. A successful read returning real PLC data is not tested end-to-end — the return value is whatever the fake says it is.

3. Mailbox serialization under concurrent reads

The driver's SemaphoreSlim serializes S7netplus calls because the S7 CPU's comm mailbox is scanned at most once per cycle. Contention behavior under real PLC latency is not exercised.

4. Variant quirks

S7-1200 vs S7-1500 vs S7-300/400 connection semantics (PG vs OP vs S7-Basic) not differentiated at test time.

5. Data types beyond the scalars

UDT fan-out, STRING with length-prefix quirks, DTL / DATE_AND_TIME, arrays of structs — not covered.

When to trust the S7 tests, when to reach for a rig

Question	Unit tests	Real PLC
"Does the address parser accept X syntax?"	yes	-
"Does the driver lifecycle hang / crash?"	yes	yes
"Does a real read against an S7-1500 return correct bytes?"	no	yes (required)
"Does mailbox serialization actually prevent PG timeouts?"	no	yes (required)
"Does a UDT fan-out produce usable member variables?"	no	yes (required)

Follow-up candidates

Snap7 server — Snap7 ships a C-library-based S7 server that could run in-CI on Linux. A pinned build + a fixture shape similar to ab_server would give S7 parity with Modbus / AB CIP coverage.
Plcsim Advanced — Siemens' paid emulator. Licensed per-seat; fits a lab rig but not CI.
Real S7 lab rig — cheapest physical PLC (CPU 1212C) on a dedicated network port, wired via self-hosted runner.

Without any of these, S7 driver correctness against real hardware is trusted from field deployments, not from the test suite.

Key fixture / config files

tests/ZB.MOM.WW.OtOpcUa.Driver.S7.Tests/ — unit tests only, no harness
src/ZB.MOM.WW.OtOpcUa.Driver.S7/S7Driver.cs — ctor takes IS7ClientFactory which tests fake; docstring lines 8-20 note the deferred integration fixture

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