# FOCAS test fixture

Coverage map + gap inventory for the FANUC FOCAS2 CNC driver.

**TL;DR: there is no integration fixture.** Every test uses a
`FakeFocasClient` injected via `IFocasClientFactory`. Fanuc's FOCAS library
(`Fwlib32.dll`) is closed-source proprietary with no public simulator;
CNC-side behavior is trusted from field deployments.

## What the fixture is

Nothing at the integration layer.
`tests/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Tests/` is unit-only. The driver ships
as Tier C (process-isolated) per `docs/v2/driver-stability.md` because the
FANUC DLL has known crash modes; tests can't replicate those in-process.

## What it actually covers (unit only)

- `FocasCapabilityTests` — data-type mapping (PMC bit / word / float,
  macro variable types, parameter types)
- `FocasReadWriteTests` — read + write against the fake, FOCAS native status
  → OPC UA StatusCode mapping
- `FocasScaffoldingTests` — `IDriver` lifecycle + multi-device routing
- `FocasPmcBitRmwTests` — PMC bit read-modify-write synchronization (per-byte
  `SemaphoreSlim`, mirrors the AB / Modbus pattern from #181)
- `FwlibNativeHelperTests` — `Focas32.dll` → `Fwlib32.dll` bridge validation
  + P/Invoke signature validation

Capability surfaces whose contract is verified: `IDriver`, `IReadable`,
`IWritable`, `ITagDiscovery`, `ISubscribable`, `IHostConnectivityProbe`,
`IPerCallHostResolver`.

## What it does NOT cover

### 1. FOCAS wire traffic

No FOCAS TCP frame is sent. `Fwlib32.dll`'s TCP-to-FANUC-gateway exchange is
closed-source; the driver trusts the P/Invoke layer per #193. Real CNC
correctness is trusted from field deployments.

### 2. Alarm / parameter-change callbacks

FOCAS has no push model — the driver polls via the shared `PollGroupEngine`.
There are no CNC-initiated callbacks to test; the absence is by design.

### 3. Macro / ladder variable types

FANUC has CNC-specific extensions (macro variables `#100-#999`, system
variables `#1000-#5000`, PMC timers / counters / keep-relays) whose
per-address semantics differ across 0i-F / 30i / 31i / 32i Series. Driver
covers the common address shapes; per-model quirks are not stressed.

### 4. Model-specific behavior

- Alarm retention across power cycles (model-specific CNC behavior)
- Parameter range enforcement (CNC rejects out-of-range writes)
- MTB (machine tool builder) custom screens that expose non-standard data

### 5. Tier-C process isolation behavior

Per driver-stability.md, FOCAS should run process-isolated because
`Fwlib32.dll` has documented crash modes. The test suite runs in-process +
only exercises the happy path + mapped error codes — a native access
violation from the DLL would take the test host down. The process-isolation
path (similar to Galaxy's out-of-process Host) has been scoped but not
implemented.

## When to trust FOCAS tests, when to reach for a rig

| Question | Unit tests | Real CNC |
| --- | --- | --- |
| "Does PMC address `R100.3` route to the right bit?" | yes | yes |
| "Does the FANUC status → OPC UA StatusCode map cover every documented code?" | yes (contract) | yes |
| "Does a real read against a 30i Series return correct bytes?" | no | yes (required) |
| "Does `Fwlib32.dll` crash on concurrent reads?" | no | yes (stress) |
| "Do macro variables round-trip across power cycles?" | no | yes (required) |

## Follow-up candidates

1. **Nothing public** — Fanuc's FOCAS Developer Kit ships an emulator DLL
   but it's under NDA + tied to licensed dev-kit installations; can't
   redistribute for CI.
2. **Lab rig** — used FANUC 0i-F simulator controller (or a retired machine
   tool) on a dedicated network; only path that covers real CNC behavior.
3. **Process isolation first** — before trusting FOCAS in production at
   scale, shipping the Tier-C out-of-process Host architecture (similar to
   Galaxy) is higher value than a CI simulator.

## Key fixture / config files

- `tests/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Tests/FakeFocasClient.cs` —
  in-process fake implementing `IFocasClient`
- `src/ZB.MOM.WW.OtOpcUa.Driver.FOCAS/FocasDriver.cs` — ctor takes
  `IFocasClientFactory`
- `docs/v2/driver-stability.md` — Tier C scope + process-isolation rationale