test(n)
  if n < 0
    got below
  else
    got above

test-nested(a, b)
  if a > 1
    if unit(-5) == ''
      got empty
      yup just lots of empty
    else
      got unit(-5px)

test-unless(n = 0)
  unless n
    padding 10px

body
  test(5px)
  test(-5px)
  test-nested(5px, -5)
  test-unless()