# Development

Requirements:
- `just`
- `jq`
- `luacheck`
- [CraftOS-PC](docs/install-craftos-pc.md) ≥ v2.8.3 — local harness for the CC:Tweaked sandbox; see [`docs/craftos_pc_glossary.md`](docs/craftos_pc_glossary.md) for CLI flags, mounting, `periphemu`, save data, and troubleshooting references.

After cloning the repository, run:

```sh
just install
```

This creates `.env` from `.env.sample` when needed and installs the local Git hooks: pre-commit runs `just test`, and pre-push runs `just ci`.

`just ci` is the full local verification entry point. Today it verifies that `craftos --version` reports v2.8.3 or newer, runs `just check` for `luacheck`, runs `just test` for CraftOS-PC headless tests, and runs the harness timeout regression guard. Use `just craftos` to launch CraftOS-PC with repo-local save data under `.craftos` and read-only mounts for `/trapos`, `/apis`, `/programs`, `/servers`, and `/startup`. `just repl` opens the same environment with `--cli` for human interactive use only; LLM agents must not run it. Use the CraftOS-PC glossary when adjusting `--headless`, `--exec`, `--script`, `--rom`, or `--mount-*` usage.

When asking an agent to commit and/or push, rely on these hooks instead of duplicating `just test` manually before Git operations: pre-commit owns `just test`, and pre-push owns `just ci`. Manual `just test` and `just ci` remain appropriate when validating changes outside a commit/push workflow.

Tests live under `tests/` and run inside CraftOS-PC through `just test`, which launches `/programs/runtest.lua`. API-level tests should use `require('/apis/libtest')({ ... })`, register cases with `testlib.test(name, fn)`, and call `testlib.run()` at the end. `libtest` tests remain normal ComputerCraft programs; the runner handles suite discovery, grouped output, and the `__TRAPOS_TEST_OK__` shell success contract. Pass `--pretty` to `just test` for grouped colored `[OK]`/`[KO]` statuses, or `--verbose` for additional runner/debug detail.

Test timeouts run in two independent layers (see [`docs/adrs/adr-0009-layered-test-timeouts.md`](docs/adrs/adr-0009-layered-test-timeouts.md)):

- **libtest per-case timeout (primary).** Each `libtest` case is cancelled after `3` seconds by default, failing with a distinct `libtest timeout` message. Override with `--timeout <seconds>`, or disable with `--no-timeout` (both forwarded by `runtest` to each case). This catches a single hung case quickly without taking down the whole run.
- **Shell watchdog (backstop).** The whole CraftOS-PC process is killed if it does not finish within `TRAP_CCLIBS_TEST_TIMEOUT_SECONDS` (`.env.sample` ships `7`; the recipe falls back to `7`). Keep it above the `3`s libtest default so libtest fires first; the watchdog only catches what Lua cannot interrupt. Override in `.env` for slower local probes.

`just test-timeout` is a self-asserting regression guard for these layers and runs automatically as part of `just ci`. It chains `just test-timeout-lua` (proves libtest cancels a slow case at 0.1s, before a 2s shell backstop) and `just test-timeout-shell` (proves the 1s shell watchdog kills a slow case run with `--no-timeout`). Both drive the `tests/harness/slow-case.lua` fixture, which is never picked up by the normal `just test` suite (`runtest` skips `tests/` subdirectories).