message: Keep fan blowing during covent tests.
  ...but close the blower valve between tests, so it's less awkward to
  fiddle with the test lung compliance.
  GPC: fan-on-during-covent-tests
diff: @@ -43,9 +43,13 @@ def run_test(test, cmd_args):
  else:
  run("set gui_fio2 21")
  - # Ensure the ventilator is blowing with some params. Edwin's request is
  - # that the ventilator is continuously on during these tests.
  - run("set gui_mode 1")
  + # Ensure the ventilator fan is on, and disconnect the fan from the system
  + # so it's not inflating the test lung. Edwin's request is that the fan
  + # doesn't have to spin up during these tests.
  + run("set forced_exhale_valve_pos 1")
  + run("set forced_blower_valve_pos 0")
  + run("set forced_blower_power 1")
  + run("set gui_mode 0")
  # Switch to this preset.
  run(f"preset {test}")
  @@ -56,6 +60,14 @@ def run_test(test, cmd_args):
  "Adjust test lung per above, then press enter. "
  "(Skip this with --nointeractive.)"
  )
  + # Unforce parameters we set above so they can be controlled by the
  + # controller. Note that we unforce the blower power *after* setting the
  + # gui_mode to 1 because if we unforced it while we were still in mode 0
  + # (i.e. "ventilator off"), the fan would momentarily spin down.
  + run("set forced_exhale_valve_pos -1")
  + run("set forced_blower_valve_pos -1")
  + run("set gui_mode 1")
  + run("set forced_blower_power -1")
  time.sleep(cmd_args.ignore_secs)
  # It would be possible to trace flow here too, but the graphs get noisy.
  