# S7 integration-test fixture — python-snap7

[python-snap7](https://github.com/gijzelaerr/python-snap7) `Server` class
wrapped in a pinned `python:3.12-slim-bookworm` image. Docker is the
only supported launch path — a fresh clone needs Docker Desktop and
nothing else.

| File | Purpose |
|---|---|
| [`Dockerfile`](Dockerfile) | `python:3.12-slim-bookworm` + `python-snap7>=2.0` + the server shim + the profile JSONs |
| [`docker-compose.yml`](docker-compose.yml) | One service per profile; currently only `s7_1500` |
| [`server.py`](server.py) | Same Python shim the native fallback uses — copy kept in the build context |
| [`profiles/*.json`](profiles/) | Area-seed definitions (DB1 / MB layouts with typed seeds) |

## Run

From the repo root:

```powershell
docker compose -f tests\Drivers\ZB.MOM.WW.OtOpcUa.Driver.S7.IntegrationTests\Docker\docker-compose.yml --profile s7_1500 up
```

Detached + stop:

```powershell
docker compose -f tests\...\Docker\docker-compose.yml --profile s7_1500 up -d
docker compose -f tests\...\Docker\docker-compose.yml --profile s7_1500 down
```

## Endpoint

- Default: `localhost:1102` (non-privileged; sidesteps Windows Firewall
  prompt + Linux's root-required bind on port 102).
- Override with `S7_SIM_ENDPOINT` to point at a real S7 CPU on `:102`.
- The driver's S7DriverOptions.Port flows through S7netplus's 5-arg
  `Plc(CpuType, host, port, rack, slot)` ctor so the non-standard port
  works end-to-end.

## Run the integration tests

In a separate shell with the container up:

```powershell
cd C:\Users\dohertj2\Desktop\lmxopcua
dotnet test tests\Drivers\ZB.MOM.WW.OtOpcUa.Driver.S7.IntegrationTests
```

`Snap7ServerFixture` probes `localhost:1102` at collection init + records
a `SkipReason` when unreachable, so tests stay green on a fresh clone
without Docker running.

## What's encoded in `profiles/s7_1500.json`

DB1 (1024 bytes) + MB (256 bytes) with typed seeds at known offsets:

| Address | Type | Seed | Purpose |
|---|---|---|---|
| `DB1.DBW0` | u16 | `4242` | read-back probe |
| `DB1.DBW10` | i16 | `-12345` | smoke i16 read |
| `DB1.DBD20` | i32 | `1234567890` | smoke i32 read |
| `DB1.DBD30` | f32 | `3.14159` | smoke f32 read (big-endian) |
| `DB1.DBX50.3` | bool | `true` | smoke bool read at bit 3 |
| `DB1.DBW100` | u16 | `0` | scratch for write-then-read |
| `DB1.STRING[200]` | S7 STRING | `"Hello"` | S7 STRING read |
| `MW0` | u16 | `1` | `S7ProbeOptions.ProbeAddress` default |

Seed types supported: `u8`, `i8`, `u16`, `i16`, `u32`, `i32`, `f32`,
`bool` (with `"bit": 0..7`), `ascii` (S7 STRING).

## Known limitations

From the `snap7.server.Server` docstring upstream:

> "Legacy S7 server implementation. Emulates a Siemens S7 PLC for testing
> and development purposes. [...] pure Python emulator implementation that
> simulates PLC behaviour for protocol compliance testing rather than
> full industrial-grade functionality."

Not exercised here — needs a lab rig:

- S7-1500 Optimized-DB symbolic access
- PG / OP / S7-Basic session-type differentiation
- PUT/GET-disabled-by-default enforcement

See [`docs/drivers/S7-Test-Fixture.md`](../../../docs/drivers/S7-Test-Fixture.md)
for the full coverage map.

## References

- [python-snap7 GitHub](https://github.com/gijzelaerr/python-snap7)
- [`docs/drivers/S7-Test-Fixture.md`](../../../docs/drivers/S7-Test-Fixture.md) — coverage map
- [`docs/v2/dev-environment.md`](../../../docs/v2/dev-environment.md) §Docker fixtures
