MCTP Server Test Plan (without I2C transport)

Branch: ocp-emea-demo

Core Insight

Server<S: Sender, const N> is generic over mctp_lib::Sender. I2C transport is just one Sender impl + a caller of server.inbound(). No mocking framework, feature flags, or cfg(test) shims needed.

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File Layout

services/mctp/server/tests/
├── common/
│   └── mod.rs         ← shared BufferSender, transfer(), DirectClient
├── echo.rs            ← already exists; refactor to use common/
├── dispatch.rs        ← already exists; add missing cases
├── server_unit.rs     ← NEW: Layer 2 unit tests
└── integration.rs     ← NEW: Layer 4 multi-fragment / concurrency

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Layer 1 — Shared Test Fixtures (common/mod.rs)

• [ ] Extract BufferSender<'_> from echo.rs and dispatch.rs into tests/common/mod.rs
• [ ] Add DroppingBufferSender (discards writes, always returns Ok) for tests that only care about inbound routing
• [ ] Extract transfer(from, to) helper into common
• [ ] Extract DirectClient<'a, S, N> into common (wraps &RefCell as MctpClient)

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Layer 2 — Server Unit Tests (server_unit.rs)

• [ ] req() + unbind() — handle allocation/deallocation
• [ ] listener() duplicate msg_type — expect AlreadyBound error
• [ ] try_recv() before any inbound() — returns None
• [ ] inbound(raw_pkt) + try_recv() — full routing path (use mctp_lib::fragment::Fragmenter to build raw pkts)
• [ ] register_recv() + update(now + timeout) — timeout fires RecvResult::TimedOut
• [ ] set_eid() / get_eid() — EID round-trip
• [ ] send() with payload > MAX_PAYLOAD — expect NoSpace error

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Layer 3 — Dispatch Unit Tests (dispatch.rs additions)

• [ ] Malformed wire request → BadArgument
• [ ] MctpOp::Send via response path (no handle, HAS_EID flag, explicit tag)
• [ ] MctpOp::Unbind for never-allocated handle → error
• [ ] MctpOp::Recv when no message ready → TimedOut (gap noted in code comment)

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Layer 4 — Integration Tests (integration.rs)

• [ ] Multi-fragment roundtrip: set get_mtu()=64, send 200-byte payload, verify reassembly
• [ ] Multiple concurrent listeners: two msg_type values, cross-deliver, verify no cross-talk
• [ ] Response-without-handle: verify tag & EID threading through echo
• [ ] Interleaved requests from two senders: tag collision avoidance

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Layer 5 — MctpClient Trait Tests (via DirectClient in echo.rs)

• [ ] MctpListener::recv() — called after inbound, returns payload
• [ ] MctpReqChannel::send() + recv() — full request-response cycle
• [ ] drop_handle mid-flight — verify outstanding entry is cleared

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Out of Scope (belongs in other crates)

Concern	Owner crate
MCTP-over-I2C framing/PEC	openprot-mctp-transport-i2c
MctpI2cReceiver::decode	openprot-mctp-transport-i2c
I2cClientBlocking mock	i2c service tests
IpcI2cClient / handle::I2C wiring	target/platform integration