def f() =
  s = metronome()
  s = bpm(s)
  output.dummy(fallible=true, s)
  thread.run.recurrent(
    {
      if
        s.bpm() != 0.
      then
        begin
          test.pass()
          (-1.)
        end
      else
        1.
      end
    }
  )
end

test.check(f)
