# ADR 0007: Use libtest For CraftOS Tests

## Status

Accepted

## Date

2026-06-08

## Context

ADR 0005 made CraftOS-PC the local harness. The first real behavior test, `tests/eventloop.lua`, proved the harness can exercise ComputerCraft APIs headlessly, but it also duplicated test-runner concerns directly in the script:

- Collect named cases.
- Print per-case progress only in verbose mode.
- Fail fast with a useful message.
- Report success only after every assertion passes, allowing the suite runner to print `__TRAPOS_TEST_OK__` once.
- Shut the ComputerCraft process down cleanly.

Those details are easy to copy incorrectly. A blocked eventloop test also showed that the shell harness needs a timeout and captured output so agentic debugging can proceed without manual interruption.

## Decision

Add `/apis/libtest.lua` as the repository's lightweight ComputerCraft test helper.

Tests under `tests/` should require it with an absolute ComputerCraft path:

```lua
local createLibTest = require('/apis/libtest');
local testlib = createLibTest({ ... });

testlib.test('example', function()
  testlib.assertEquals(1 + 1, 2);
end);

testlib.run();
```

`libtest` intentionally stays small. It provides named cases, `assertEquals`, `assertTrue`, `assertErrors`, optional case-status report output consumed by the suite runner, and failure reporting.

`/programs/runtest.lua` owns suite-level concerns: test discovery, invoking test scripts, grouped pretty output, verbose runner diagnostics, the `__TRAPOS_TEST_OK__` success marker, and optional shutdown. The shell harness keeps only host-level concerns: CraftOS-PC launch flags, read-only mounts, stdout capture, and timeout enforcement through `TRAP_CCLIBS_TEST_TIMEOUT_SECONDS`.

## Consequences

- New deterministic behavior should get as many useful CraftOS-PC tests as practical.
- Tests that require human validation, such as complex turtle motion, in-game UX feel, or visual approval, may be skipped, but deterministic pieces should still get unit-style non-regression coverage.
- Test scripts remain normal ComputerCraft programs, not standalone Lua tests. They can run through `just test`, `/programs/runtest.lua`, or direct in-game execution when copied with their dependencies.
- `libtest` lives under `/apis` and is listed in `manifest.json`, so it can be required consistently in the mounted CraftOS-PC environment.
- The `__TRAPOS_TEST_OK__` marker remains the single shell-level success contract and is owned by `/programs/runtest.lua`.

## Future Work

- Add more assertions only when tests need them; avoid growing a large framework.
- Add more runner filters only when useful; keep the common no-argument path as automatic `tests/*.lua` discovery.
- Explore GitHub Actions with the Linux CraftOS-PC AppImage after local coverage is broader.