Bootstrap DD3 Rust port workspace with host-first compatibility tests

docs/TEST_STRATEGY.md

@@ -0,0 +1,63 @@
+# 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`