test_signs_in_rationals = ->
  run_test [

    # I found out about basic mistakes in
    # these very very late, better to
    # have those tests early on.

    "1/1",
    "1",

    "-1/1",
    "-1",

    "1/(-1)",
    "-1",

    "(-1)/(-1)",
    "1",

  ]