test: characterize the hidpp v20 matcher and cover the CLI

[AprilNEA]

Summary

Closes the two long-standing test gaps flagged in the engineering audit: the HID++ 2.0 send/response-matcher path in the vendored hidpp fork had no characterization tests, and openlogi-cli had 2 tests for ~965 lines. All changes are purely additive #[cfg(test)] modules — zero production lines modified.

Changes

• hidpp: characterization tests for the v20 correlation layer (protocol/v20.rs::send_v20 over the predicate-based HidppChannel::send), reusing the existing MockRawHidChannel harness: header-field correlation against interleaved decoys, broadcast events not consuming pending requests, 0xFF error-frame decoding (mapped code → Hidpp20Error::Feature, unmapped code → UnsupportedResponse), and the width-agnostic matching quirk (a Long reply to a Short request is accepted) pinned as current behavior.
• cli: 30 tests covering clap parsing (debug_assert, arg conflicts, NonZeroU8 bounds, value-enum mapping), diag message selection, DPI list-vs-range summarization, lighting color validation (rejects before any device I/O), optional-asset classification incl. two pinned quirks, and list output formatting. Pure dispatch glue and hardware-seam functions were deliberately left untested (tautological or requiring prod changes).

Found while writing tests, recorded here rather than fixed (test-only PR): the unreachable map_err in diag/lighting.rs color parsing, and is_optional_asset's loose front_ext* prefix match.

Testing

• cargo test -p openlogi-hidpp -p openlogi-cli — 157 + 30 passed, 0 failed
• cargo clippy -p openlogi-cli --all-targets -- -D warnings — clean
• Not runtime-tested on hardware (all tests run against mocks or pre-I/O validation paths).

[greptile-apps]

Greptile Summary

This PR is purely additive test coverage — zero production lines are modified. It adds characterization tests for the HID++ 2.0 send/response matcher in openlogi-hidpp and ~30 new tests for the CLI layer covering Clap parsing, diagnostic message selection, DPI range summarization, color validation, optional-asset classification, and list output formatting.

• crates/openlogi-hidpp/src/channel.rs: 5 new #[cfg(test)] tests for send_v20, exercising header-field correlation against decoys, broadcast-event pass-through, width-agnostic matching, and 0xFF error-frame decoding.
• crates/openlogi-cli/src/**: 30 tests across lib.rs, diag/, assets/sync.rs, and cmd/list.rs. Known quirks are explicitly called out as pinned-current-behaviour.

Confidence Score: 5/5

All changes are additive test-only code; no production lines are touched, so there is no risk of regression.

The PR adds only #[cfg(test)] modules. The one gap identified — a missing function_id decoy in a characterization test — does not affect production behaviour in any way.

crates/openlogi-hidpp/src/channel.rs — the decoy set in send_v20_matches_response_by_header_ignoring_unrelated_messages does not cover all four header fields.

Important Files Changed

Filename	Overview
crates/openlogi-hidpp/src/channel.rs	Adds 5 characterization tests for the v20 send/matcher path; one test's comment claims all four header fields are covered by decoys but the function_id field has no corresponding decoy.
crates/openlogi-cli/src/lib.rs	Adds 7 Clap parsing tests: structural validation, bare invocation, conflict detection, NonZeroU8 rejection, value-enum mapping and flag round-trips.
crates/openlogi-cli/src/cmd/assets/sync.rs	Adds 6 tests for is_optional_asset, including two explicitly-pinned quirk tests.
crates/openlogi-cli/src/cmd/diag/dpi.rs	Adds 2 tests pinning the list-vs-range boundary in summarize_dpi at exactly 12 values.
crates/openlogi-cli/src/cmd/diag/lighting.rs	Adds 2 async tests exercising pre-I/O color validation.
crates/openlogi-cli/src/cmd/diag/mod.rs	Adds 4 tests for the no_match_err error-message builder, covering all four branches.
crates/openlogi-cli/src/cmd/list.rs	Adds 7 tests for format_device, format_battery, and format_model.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant Test
    participant HidppChannel
    participant ReadThread
    participant Listener

    Test->>HidppChannel: send_v20(request)
    Note over HidppChannel: registers oneshot waiter
    HidppChannel-->>ReadThread: (background loop)

    Test->>ReadThread: feed decoys (wrong_device / wrong_feature / wrong_sw_id)
    ReadThread->>ReadThread: predicate false - skip waiter
    ReadThread->>Listener: "notify(decoy, matched=false)"

    Test->>ReadThread: feed response (header matches)
    ReadThread->>HidppChannel: resolve oneshot
    ReadThread->>Listener: "notify(response, matched=true)"

    Note over Test: wait_for_event_count before asserting listener events

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sequenceDiagram
    participant Test
    participant HidppChannel
    participant ReadThread
    participant Listener

    Test->>HidppChannel: send_v20(request)
    Note over HidppChannel: registers oneshot waiter
    HidppChannel-->>ReadThread: (background loop)

    Test->>ReadThread: feed decoys (wrong_device / wrong_feature / wrong_sw_id)
    ReadThread->>ReadThread: predicate false - skip waiter
    ReadThread->>Listener: "notify(decoy, matched=false)"

    Test->>ReadThread: feed response (header matches)
    ReadThread->>HidppChannel: resolve oneshot
    ReadThread->>Listener: "notify(response, matched=true)"

    Note over Test: wait_for_event_count before asserting listener events

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_{Reviews (2): Last reviewed commit: "test(hidpp): wait for listener delivery ..." | Re-trigger Greptile}