test(harness): run timeout-layer checks in ci

- Add fast `test-timeout` guard chaining `test-timeout-lua`/`-shell`
- Wire `test-timeout` into `just ci` for harness regression coverage
- Consolidate fixtures into single `tests/harness/slow-case.lua`
- Tighten timeouts (libtest 2s / shell watchdog 3s) so each check is ~3s
- Update ADR-0009 and DEVELOPMENT.md for the new recipes and ci wiring

DEVELOPMENT.md

@@ -23,4 +23,4 @@ Test timeouts run in two independent layers (see [`docs/adrs/adr-0009-layered-te
 - **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-5s` and `just test-timeout-10s` are self-asserting harness checks for these layers (fixtures under `tests/harness/`, not part of `just test`): the first proves libtest cancels a 5s case at 3s, the second proves the shell watchdog kills a 10s case run with `--no-timeout`.
+`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 2s, before a generous 5s shell backstop) and `just test-timeout-shell` (proves the 3s 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).

Justfile

@@ -100,6 +100,7 @@ repl:
 # Local CI entry point used by Git hooks. Pass args through to `test`.
 ci *args: check-craftos check
     @just test {{args}}
+    @just test-timeout
 
 # Run CraftOS-PC headless integration tests. Pass `--pretty` for grouped output.
 test *args:
@@ -204,13 +205,16 @@ _timeout-fixture script shell_timeout extra_flag expect: check-install
     rm -rf "$data_dir"
     exit "$rc"
 
-# Prove the libtest (Lua) timeout layer: a 5s case is cancelled at the 3s
-# default, before the generous 30s shell watchdog can fire.
-test-timeout-5s: (_timeout-fixture "/tests/harness/timeout-5s.lua" "30" "" "lua")
+# Prove the libtest (Lua) timeout layer: libtest cancels the slow case at 2s,
+# before the generous 5s shell watchdog backstop can fire.
+test-timeout-lua: (_timeout-fixture "/tests/harness/slow-case.lua" "5" "'--timeout', '2'," "lua")
 
-# Prove the shell watchdog backstop: a 10s case runs with the libtest timeout
-# bypassed (--no-timeout), so the 5s shell watchdog kills the whole process.
-test-timeout-10s: (_timeout-fixture "/tests/harness/timeout-10s.lua" "5" "'--no-timeout'," "shell")
+# Prove the shell watchdog backstop: the slow case runs with the libtest timeout
+# bypassed (--no-timeout), so the 3s shell watchdog kills the whole process.
+test-timeout-shell: (_timeout-fixture "/tests/harness/slow-case.lua" "3" "'--no-timeout'," "shell")
+
+# Fast regression guard for both timeout layers. Wired into `ci`.
+test-timeout: test-timeout-lua test-timeout-shell
 
 # Lint all Lua source with luacheck.
 check: check-luacheck

docs/adrs/adr-0009-layered-test-timeouts.md

@@ -48,7 +48,8 @@ confused.
 - Never commit a hanging or intentionally-slow test to `tests/`: it would fail every run.
 - Intentionally-slow fixtures that exercise the harness itself live in `tests/harness/`.
   `runtest` discovery skips subdirectories, so they never run with the normal suite; they
-  are driven only by dedicated recipes (`just test-timeout-5s`, `just test-timeout-10s`).
+  are driven only by dedicated recipes (`just test-timeout-lua`, `just test-timeout-shell`,
+  aggregated by `just test-timeout`).
 - Use `--no-timeout` only for harness fixtures that must outlive the libtest layer to prove
   the shell watchdog, never for ordinary tests.
 
@@ -56,10 +57,12 @@ confused.
 
 - A hung case now fails in ~3s with a per-case message instead of taking down the whole
   process anonymously.
-- The two `test-timeout-*` recipes are self-asserting harness tests: `test-timeout-5s`
-  proves Layer 1 (libtest cancels a 5s case before the watchdog), `test-timeout-10s` proves
-  Layer 2 (the watchdog kills a 10s case with libtest bypassed). They are intentionally
-  excluded from `ci`/`test`.
+- `just test-timeout` is a self-asserting harness regression guard wired into `just ci`. It
+  chains `test-timeout-lua` (Layer 1: libtest cancels the slow case at 2s, before a generous
+  5s shell backstop) and `test-timeout-shell` (Layer 2: the 3s watchdog kills the slow case
+  with libtest bypassed). Both drive a single `tests/harness/slow-case.lua` fixture; the
+  tight timeouts — not the fixture's sleep length — decide which layer fires, so each check
+  finishes in ~3s and the harness itself is covered against regressions on every `ci`.
 - `libtest` stays a normal ComputerCraft program: `parallel` and `sleep` are sandbox
   globals, so the timeout works in CraftOS-PC and in-game alike.
 

tests/harness/slow-case.lua

@@ -0,0 +1,16 @@
+-- Harness fixture (NOT auto-discovered: lives under tests/harness/).
+-- A single case that sleeps well past any harness timeout. The driving recipe
+-- decides which layer cancels it: `test-timeout-lua` lets libtest fire via
+-- `--timeout`, `test-timeout-shell` bypasses libtest (`--no-timeout`) so the
+-- shell watchdog kills the process. See `just test-timeout`.
+local createLibTest = require('/apis/libtest');
+
+local testlib = createLibTest({ ... });
+
+testlib.test('sleeps past the harness timeout', function()
+  testlib.log('about to sleep 10s; the active harness timeout should cancel this first');
+  sleep(10);
+  testlib.assertTrue(true); -- never reached: a timeout layer cancels first
+end);
+
+testlib.run();

tests/harness/timeout-10s.lua

@@ -1,14 +0,0 @@
--- Harness fixture (NOT auto-discovered: lives under tests/harness/).
--- Sleeps 10s with the libtest timeout bypassed (--no-timeout), proving the
--- shell watchdog is still the backstop. Driven by `just test-timeout-10s`.
-local createLibTest = require('/apis/libtest');
-
-local testlib = createLibTest({ ... });
-
-testlib.test('sleeps past the shell watchdog', function()
-  testlib.log('about to sleep 10s with the libtest timeout disabled');
-  sleep(10);
-  testlib.assertTrue(true); -- never reached: shell watchdog kills the process
-end);
-
-testlib.run();

tests/harness/timeout-5s.lua

@@ -1,14 +0,0 @@
--- Harness fixture (NOT auto-discovered: lives under tests/harness/).
--- Sleeps past the 3s libtest default timeout but under the 7s shell watchdog,
--- proving the libtest layer cancels the case first. Driven by `just test-timeout-5s`.
-local createLibTest = require('/apis/libtest');
-
-local testlib = createLibTest({ ... });
-
-testlib.test('sleeps past the libtest timeout', function()
-  testlib.log('about to sleep 5s; libtest should cancel this case at 3s');
-  sleep(5);
-  testlib.assertTrue(true); -- never reached: libtest cancels first
-end);
-
-testlib.run();