Layered Test Suite Architecture (PR‑8.3)

Overview

- Tests are organized by runtime layer to isolate failures and clarify ownership of behavior.
- Location: `crates/dev/prometeu-layer-tests/tests/`

Layers and representative tests

1. Bytecode encode/decode
   - `bytecode_encode_decode.rs` — round‑trip decoding for edge immediates and structure.
2. Verifier
   - `verifier_closure_reject.rs` — rejects `CALL_CLOSURE` when TOS is not a closure.
   - Rule: verifier tests never run the VM.
3. VM execution
   - `vm_exec_valid.rs` — executes a tiny valid program; assumes verified input.
   - Rule: VM tests do not depend on the verifier; they prepare ROM directly.
4. GC behavior
   - `gc_collect_unreachable.rs` — unrooted closure is reclaimed; rooted one survives.
5. Scheduler behavior
   - `scheduler_determinism.rs` — deterministic FIFO ordering for same‑tick wakeups.

Running the layered suite

- Run just the layered tests: `cargo test -p prometeu-layer-tests`
- Run the entire workspace: `cargo test`

Host debugger socket tests

- The host debugger integration tests in `crates/host/prometeu-host-desktop-winit/src/runner.rs` open localhost TCP ports and are marked `#[ignore]` in the default test flow.
- This keeps `cargo test --workspace --all-targets --all-features --no-fail-fast` green in restricted environments that forbid `TcpListener::bind`.
- Run the socket-dependent suite explicitly with `make test-debugger-socket` or `cargo test -p prometeu-host-desktop-winit --lib -- --ignored`.
- These tests must still run in at least one official environment that permits localhost bind/connect.

Separation of concerns

- No cross‑layer assumptions in these tests.
- Verifier tests: no `VirtualMachine` execution.
- VM tests: assume pre‑verified bytecode; interact via public VM APIs only.
- GC and Scheduler tests: exercise their public APIs directly, without booting the VM.

DRY helpers

- Shared utilities should live in `crates/dev/prometeu-test-support` when needed. The current minimal suite avoids duplication by using tiny local helpers.