(.module:
  [library
   [lux #*
    ["_" test (#+ Test)]
    [abstract
     [monad (#+ do)]]
    [math
     ["." random (#+ Random)]]]]
  [\\library
   ["." /]])

(def: .public (spec (^open "\.") gen_sample)
  (All [a] (-> (/.Enum a) (Random a) Test))
  (do random.monad
    [sample gen_sample]
    (<| (_.for [/.Enum])
        ($_ _.and
            (_.test "Successor and predecessor are inverse functions."
                    (and (\= (|> sample \succ \pred)
                             sample)
                         (\= (|> sample \pred \succ)
                             sample)
                         (not (\= (\succ sample)
                                  sample))
                         (not (\= (\pred sample)
                                  sample))))
            ))))