On benches where the Owon PSU powers the ECU, every per-file PSU
fixture that closed the port (sending 'output 0' on close) browned
out the bench between modules — every MUM test that ran after a
closed PSU connection failed with "ECU not responding".
New tests/hardware/conftest.py provides three session-scoped
fixtures:
- _psu_or_none: tolerant. Opens the Owon PSU once via resolve_port,
parks at config.power_supply.set_voltage / set_current, enables
output. Yields the live OwonPSU or None. Closes (with
safe_off_on_close=True) at session end — the bench ends safely
de-energized.
- _psu_powers_bench: autouse=True. Realizes _psu_or_none so even
tests that don't request `psu` by name benefit from the
session-level power-up. No-op if PSU isn't configured.
- psu: public. Skips cleanly when the PSU isn't reachable.
Contract for tests:
- request `psu` if you need to read measurements or change voltage
- restore nominal voltage in your finally block
- MUST NOT call psu.set_output(False) (would brown out the bench)
- MUST NOT call psu.close() (the session fixture owns it)
test_owon_psu.py becomes read-only:
- removed the local module-scoped psu fixture
- removed the set_output toggle (would have killed the session)
- now validates IDN, output_is_on(), and parsed measurements
against the always-on PSU. Renamed to
test_owon_psu_idn_and_measurements to reflect the new shape.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
