0014. Test with a fake build, one CI job per scenario

• Status: accepted
• Date: 2026-10-21

Context

A real server build must never be downloaded, re-hosted or committed by the tests, and it refuses to start without a license key, which CI does not have. The role’s main promises (the unit starts, the health check, update, automatic rollback and rollback) can only be shown with a process that starts and answers. ADR 0006 runs one Molecule job per role and platform from the default scenario only; a role with a second scenario would leave it untested in CI.

Considered options

1. Test with the unit enabled but not started, and only check files.
2. A fake build: tests/fake-artifact/build.py writes an fx.tar.xz with the layout of a real build whose run.sh starts a small Python standard-library HTTP server that reads server.cfg and answers /info.json, /dynamic.json, /players.json and /perf/ (basic auth) with synthetic data, and a deliberately broken variant.
3. A mock HTTP server outside the unit, started by the test.

Decision

Chosen option 2, because the unit, ExecStart, the hardening and the current link are then really used. The fake refuses to start without sv_licenseKey, never prints it and logs no client addresses; tests/test_fake_fxserver.py pins its behaviour. This extends ADR 0006: scripts/molecule_scenarios.py lists every scenario of a role (default first, which stays mandatory) on both platforms, and CI runs one molecule-scenario (<role>, <scenario>, <platform>) job each. Instance names are gs-<role>-<platform> for default and gs-<role>-<scenario>-<platform> otherwise; a name that two entries would share fails the list.

Consequences

• Good: the update, the automatic rollback and the rollback run end to end on every pull request.
• Good: a new scenario is tested by adding its folder; CI needs no change.
• Bad: the fake models only the fields the tests use; real answers may differ, and the real build (with its own needs under the hardened unit) is only tested by hand.
• Bad: two more CI jobs per extra scenario.