Joseph Doherty
d686e12123
STALE-STATUS: TL;DR claimed "Wire-level round-trip against ab_server PCCC
mode currently fails with BadCommunicationError on read/write (verified
2026-04-20)." Docker/README.md §Known limitations explicitly states the
root cause was ab_server's empty-CIP-path gate, not a pccc.c gap, and that
N/F/L files round-trip cleanly with the /1,0 path. AbLegacyReadSmokeTests.cs
confirms tests pass against the fixture. Rewrote TL;DR + What-the-fixture-is
opening to reflect current passing state; residual gap is only B3 bit-file
writes (0x803D0000).
STALE-STATUS: Lifecycle probe listed as localhost:44818.
AbLegacyServerFixture.cs:57,119 default is 10.100.0.35:44818 (shared Docker
host, migrated 2026-04-28). Fixed.
INLINE COMPLETENESS: Follow-up item 1 phrased as future work ("smoke suite
passes today for N/F/L…"); tightened to describe the current passing state
and narrowed the remaining action to the bit-file write gap.
Verified: python3 .docs-audit/check_links.py — zero rows for this doc.
128 lines
6.1 KiB
Markdown
128 lines
6.1 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/Drivers/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`). The smoke tests pass
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for N-file (Int16), F-file (Float32), and L-file (Int32) reads across all
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three families when `AB_LEGACY_CIP_PATH=1,0` (the default). The earlier
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`BadCommunicationError` was traced to `ab_server` requiring a non-empty CIP
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routing path before forwarding to the PCCC dispatcher — the `/1,0` workaround
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resolves it (see `Docker/README.md §Known limitations`). Residual gap: bit-file
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writes (`B3:0/5`) still surface `0x803D0000` against `ab_server`. Unit tests
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via `FakeAbLegacyTag` carry full contract coverage for all paths.
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## What the fixture is
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**Integration layer** (task #224):
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`tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.IntegrationTests/` with
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`AbLegacyServerFixture` (TCP-probes `10.100.0.35:44818` — the shared Docker
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host; override with `AB_LEGACY_ENDPOINT`) + three smoke tests (parametric read
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across families, SLC500 write-then-read). Reuses the AB CIP
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`otopcua-ab-server:libplctag-release` image via a relative `build:` context in
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`Docker/docker-compose.yml` — one image, different `--plc` flags. See
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`Docker/README.md §Known limitations` for the CIP-path gate + bit-file write
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gap.
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**Unit layer**: `tests/Drivers/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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- `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. **Close residual ab_server bit-file write gap** — N (Int16), F (Float32),
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and L (Int32) files round-trip cleanly across SLC500 / MicroLogix / PLC-5
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modes with the `/1,0` cip-path workaround in place. Remaining gap: bit-file
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writes (`B3:0/5`) surface `0x803D0000` against `ab_server --plc=SLC500`.
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Contributing a patch to `libplctag/libplctag` to close this would remove
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the last Docker-vs-hardware divergence for bit writes.
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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/Drivers/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/Drivers/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/Drivers/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/Drivers/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/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.Tests/FakeAbLegacyTag.cs` —
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in-process fake + factory
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- `src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy/AbLegacyDriver.cs` — scope remarks
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at the top of the file
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