105 lines
4.0 KiB
Markdown
105 lines
4.0 KiB
Markdown
# S7 integration-test fixture — python-snap7
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[python-snap7](https://github.com/gijzelaerr/python-snap7) `Server` class
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wrapped in a pinned `python:3.12-slim-bookworm` image. Docker is the
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only supported launch path — a fresh clone needs Docker Desktop and
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nothing else.
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| File | Purpose |
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| [`Dockerfile`](Dockerfile) | `python:3.12-slim-bookworm` + `python-snap7>=2.0` + the server shim + the profile JSONs |
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| [`docker-compose.yml`](docker-compose.yml) | One service per profile; currently only `s7_1500` |
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| [`server.py`](server.py) | Same Python shim the native fallback uses — copy kept in the build context |
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| [`profiles/*.json`](profiles/) | Area-seed definitions (DB1 / MB layouts with typed seeds) |
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## Run
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From the repo root:
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```powershell
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docker compose -f tests\ZB.MOM.WW.OtOpcUa.Driver.S7.IntegrationTests\Docker\docker-compose.yml --profile s7_1500 up
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```
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Detached + stop:
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```powershell
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docker compose -f tests\...\Docker\docker-compose.yml --profile s7_1500 up -d
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docker compose -f tests\...\Docker\docker-compose.yml --profile s7_1500 down
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```
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## Endpoint
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- Default: `localhost:1102` (non-privileged; sidesteps Windows Firewall
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prompt + Linux's root-required bind on port 102).
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- Override with `S7_SIM_ENDPOINT` to point at a real S7 CPU on `:102`.
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- The driver's S7DriverOptions.Port flows through S7netplus's 5-arg
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`Plc(CpuType, host, port, rack, slot)` ctor so the non-standard port
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works end-to-end.
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## Run the integration tests
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In a separate shell with the container up:
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```powershell
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cd C:\Users\dohertj2\Desktop\lmxopcua
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dotnet test tests\ZB.MOM.WW.OtOpcUa.Driver.S7.IntegrationTests
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```
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`Snap7ServerFixture` probes `localhost:1102` at collection init + records
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a `SkipReason` when unreachable, so tests stay green on a fresh clone
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without Docker running.
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## What's encoded in `profiles/s7_1500.json`
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DB1 (1024 bytes) + MB (256 bytes) with typed seeds at known offsets:
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| Address | Type | Seed | Purpose |
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| `DB1.DBW0` | u16 | `4242` | read-back probe |
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| `DB1.DBW10` | i16 | `-12345` | smoke i16 read |
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| `DB1.DBD20` | i32 | `1234567890` | smoke i32 read |
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| `DB1.DBD30` | f32 | `3.14159` | smoke f32 read (big-endian) |
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| `DB1.DBX50.3` | bool | `true` | smoke bool read at bit 3 |
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| `DB1.DBW100` | u16 | `0` | scratch for write-then-read |
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| `DB1.STRING[200]` | S7 STRING | `"Hello"` | S7 STRING read |
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| `MW0` | u16 | `1` | `S7ProbeOptions.ProbeAddress` default |
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Seed types supported: `u8`, `i8`, `u16`, `i16`, `u32`, `i32`, `f32`,
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`bool` (with `"bit": 0..7`), `ascii` (S7 STRING).
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## Negotiated PDU size
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Snap7's `Server` always negotiates a **fixed 240-byte PDU** during the
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COTP/S7comm handshake (the legacy default — Snap7 does not implement the
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S7-1500 extended-PDU negotiation). The S7 driver surfaces this value
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through `DriverHealth.Diagnostics["S7.NegotiatedPduSize"]`, exercised by
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`S7_1500DiagnosticsTests.Driver_exposes_negotiated_pdu_size_post_init`.
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Operators inspecting a driver against this fixture should therefore see
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`S7.NegotiatedPduSize = 240`. Real S7-1500 CPUs running the extended PDU
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report 480 or 960; that branch is hardware-only and not exercised here.
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## Known limitations
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From the `snap7.server.Server` docstring upstream:
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> "Legacy S7 server implementation. Emulates a Siemens S7 PLC for testing
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> and development purposes. [...] pure Python emulator implementation that
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> simulates PLC behaviour for protocol compliance testing rather than
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> full industrial-grade functionality."
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Not exercised here — needs a lab rig:
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- S7-1500 Optimized-DB symbolic access
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- PG / OP / S7-Basic session-type differentiation
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- PUT/GET-disabled-by-default enforcement
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See [`docs/drivers/S7-Test-Fixture.md`](../../../docs/drivers/S7-Test-Fixture.md)
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for the full coverage map.
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## References
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- [python-snap7 GitHub](https://github.com/gijzelaerr/python-snap7)
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- [`docs/drivers/S7-Test-Fixture.md`](../../../docs/drivers/S7-Test-Fixture.md) — coverage map
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- [`docs/v2/dev-environment.md`](../../../docs/v2/dev-environment.md) §Docker fixtures
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