# Test Strategy

This repository uses four host-side test pillars to preserve compatibility and deterministic behavior.

## 1) Byte-exact protocol compatibility
- Crate: `dd3_protocol`
- Scope:
  - CRC16-CCITT vectors
  - Frame encode/decode byte identity
  - ACK payload byte identity
  - Chunk reassembly deterministic reset semantics
  - Payload schema v3 decode/re-encode golden vectors
- Fixtures:
  - `fixtures/protocol/frames/*.bin`
  - `fixtures/protocol/chunks/*.bin`
  - `fixtures/protocol/payload_v3/*.bin`

## 2) Contract stability
- Crate: `dd3_contracts`
- Scope:
  - Home Assistant discovery JSON contract
  - MQTT state JSON key/semantic stability
  - CSV header and line format stability
  - sanitize/html/url behavior including adversarial inputs
  - manufacturer drift guard
- Fixtures:
  - `fixtures/contracts/ha_discovery/*.json`
  - `fixtures/contracts/mqtt_state/*.json`
  - `fixtures/contracts/sd_csv/*.csv`

## 3) Deterministic state machine behavior
- Crates: `dd3_core`, `dd3_sim`
- Scope:
  - unsynced sender sync-request cadence
  - time bootstrap unlock via valid ACK
  - stop-and-wait retry behavior under loss/backpressure
  - ACK mismatch handling
  - duplicate-batch suppression on receiver publish/log paths

## 4) Robustness fuzz/property checks
- `fuzz/` targets:
  - `frame_decode`
  - `chunk_stream_ingest`
  - `payload_decode_v3`
  - `sanitize_device_id`
  - `url_encode_component`

## Running Tests (host only)
Prerequisite: install Rust toolchain (`rustup`, `cargo`, `rustfmt`, `clippy`).

- Workspace tests:
  - `make test`
  - or `cargo test --workspace`
- Lint:
  - `make lint`
- Fuzz smoke (optional, skipped when `cargo-fuzz` missing):
  - `make fuzz-smoke`

## Fixture Refresh
- Ensure baseline subtree exists at `vendor/dd3-cpp` pinned to baseline commit.
- Run:
  - `cargo run -p xtask -- sync-fixtures`
  - `cargo run -p xtask -- verify-fixture-sources`