135 lines
6.5 KiB
Markdown
135 lines
6.5 KiB
Markdown
# AB Legacy test fixture
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Coverage map + gap inventory for the AB Legacy (PCCC) driver — SLC 500 /
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MicroLogix / PLC-5 / LogixPccc-mode.
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**TL;DR:** Docker integration-test scaffolding lives at
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`tests/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.IntegrationTests/` (task #224),
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reusing the AB CIP `ab_server` image in PCCC mode with per-family
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compose profiles (`slc500` / `micrologix` / `plc5`). Scaffold passes
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the skip-when-absent contract cleanly. **Wire-level round-trip against
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`ab_server` PCCC mode currently fails** with `BadCommunicationError`
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on read/write (verified 2026-04-20) — ab_server's PCCC server-side
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coverage is narrower than libplctag's PCCC client expects. The smoke
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tests target the correct shape for real hardware + should pass when
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`AB_LEGACY_ENDPOINT` points at a real SLC 5/05 / MicroLogix. Unit tests
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via `FakeAbLegacyTag` still carry the contract coverage.
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## What the fixture is
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**Integration layer** (task #224, scaffolded with a known ab_server
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gap):
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`tests/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.IntegrationTests/` with
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`AbLegacyServerFixture` (TCP-probes `localhost:44818`) + three smoke
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tests (parametric read across families, SLC500 write-then-read). Reuses
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the AB CIP `otopcua-ab-server:libplctag-release` image via a relative
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`build:` context in `Docker/docker-compose.yml` — one image, different
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`--plc` flags. See `Docker/README.md` §Known limitations for the
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ab_server PCCC round-trip gap + resolution paths.
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**Unit layer**: `tests/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.Tests/` is
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still the primary coverage. All tests tagged `[Trait("Category", "Unit")]`.
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The driver accepts `IAbLegacyTagFactory` via ctor DI; every test
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supplies a `FakeAbLegacyTag`.
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## What it actually covers (unit only)
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- `AbLegacyAddressTests` — PCCC address parsing for SLC / MicroLogix / PLC-5
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/ LogixPccc-mode (`N7:0`, `F8:12`, `B3:0/5`, etc.)
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- `AbLegacyArrayTests` — PR 7 array contiguous-block addressing: parser
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positives + rejects for `,N` / `[N]` suffixes, options-override
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(`ArrayLength`), driver `IsArray` discovery, and array decoding for N / F /
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L / B files (Rockwell convention: one BOOL per word for `B3:0,10`). Latency
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benchmark against the Docker fixture is a perf-flagged integration case in
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`AbLegacyArrayReadTests` — runs only when ab_server is reachable.
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- `AbLegacyCapabilityTests` — data type mapping, read-only enforcement
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- `AbLegacyReadWriteTests` — read + write happy + error paths against the fake
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- `AbLegacyBitRmwTests` — bit-within-DINT read-modify-write serialization via
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per-parent `SemaphoreSlim` (mirrors the AB CIP + FOCAS PMC-bit pattern from #181)
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- `AbLegacyHostAndStatusTests` — probe + host-status transitions driven by
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fake-returned statuses
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- `AbLegacyDriverTests` — `IDriver` lifecycle
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Capability surfaces whose contract is verified: `IDriver`, `IReadable`,
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`IWritable`, `ITagDiscovery`, `ISubscribable`, `IHostConnectivityProbe`,
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`IPerCallHostResolver`.
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## What it does NOT cover
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### 1. Wire-level PCCC
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No PCCC frame is sent by the test suite. libplctag's PCCC subset (DF1,
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ControlNet-over-EtherNet, PLC-5 native EtherNet) is untested here;
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driver-side correctness depends on libplctag being correct.
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### 2. Family-specific behavior
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- SLC 500 timeout + retry thresholds (SLC's comm module has known slow-response
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edges) — unit fakes don't simulate timing.
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- MicroLogix 1100 / 1400 max-connection-count limits — not stressed.
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- PLC-5 native EtherNet connection setup (PCCC-encapsulated-in-CIP vs raw
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CSPv4) — routing covered at parse level only.
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### 3. Multi-device routing
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`IPerCallHostResolver` contract is verified; real PCCC wire routing across
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multiple gateways is not.
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### 4. Alarms / history
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PCCC has no alarm object + no history object. Driver doesn't implement
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`IAlarmSource` or `IHistoryProvider` — no test coverage is the correct shape.
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### 5. File-type coverage
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PCCC has many file types (N, F, B, T, C, R, S, ST, A) — the parser tests
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cover the common ones but uncommon ones (`R` counters, `S` status files,
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`A` ASCII strings) have thin coverage.
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## When to trust AB Legacy tests, when to reach for a rig
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| Question | Unit tests | Real PLC |
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| --- | --- | --- |
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| "Does `N7:0/5` parse correctly?" | yes | - |
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| "Does bit-in-word RMW serialize concurrent writers?" | yes | yes |
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| "Does the driver lifecycle hang / crash?" | yes | yes |
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| "Does a real read against an SLC 500 return correct bytes?" | no | yes (required) |
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| "Does MicroLogix 1100 respect its connection-count cap?" | no | yes (required) |
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| "Do PLC-5 ST-files round-trip correctly?" | no | yes (required) |
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## Follow-up candidates
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1. **Expand ab_server PCCC coverage** — the smoke suite passes today
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for N (Int16), F (Float32), and L (Int32) files across SLC500 /
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MicroLogix / PLC-5 modes with the `/1,0` cip-path workaround in
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place. Known residual gap: bit-file writes (`B3:0/5`) surface
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`0x803D0000`. Contributing a patch to `libplctag/libplctag` to close
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this + documenting ab_server's empty-path rejection in its README
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would remove the last Docker-vs-hardware divergences.
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2. **Rockwell RSEmulate 500 golden-box tier** — Rockwell's real emulator
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for SLC/MicroLogix/PLC-5. Would close UDT-equivalent (integer-file
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indirection), timer/counter decomposition, and real ladder execution
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gaps. Costs: RSLinx OEM license, Windows-only, Hyper-V conflict
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matching TwinCAT XAR + Logix Emulate, no clean PR-diffable project
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format (SLC/ML save as binary `.RSS`). Scaffold like the Logix
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Emulate tier when operationally worth it.
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3. **Lab rig** — used SLC 5/05 or MicroLogix 1100 on a dedicated
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network; parts are end-of-life but still available. PLC-5 +
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LogixPccc-mode behaviour + DF1 serial need specific controllers.
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## Key fixture / config files
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- `tests/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.IntegrationTests/AbLegacyServerFixture.cs`
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— TCP probe + skip attributes + env-var parsing
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- `tests/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.IntegrationTests/AbLegacyReadSmokeTests.cs`
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— wire-level smoke tests; pass against the ab_server Docker fixture
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with `AB_LEGACY_COMPOSE_PROFILE` set to the running container
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- `tests/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.IntegrationTests/Docker/docker-compose.yml`
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— compose profiles reusing AB CIP Dockerfile
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- `tests/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.IntegrationTests/Docker/README.md`
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— known-limitations write-up + resolution paths
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- `tests/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.Tests/FakeAbLegacyTag.cs` —
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in-process fake + factory
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- `src/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy/AbLegacyDriver.cs` — scope remarks
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at the top of the file
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