(.using
 [library
  [lux "*"
   [abstract
    [monad (.only do)]]
   [data
    ["[0]" identity (.only Identity)]]
   [math
    ["[0]" random]
    [number
     ["n" nat]]]
   ["_" test (.only Test)]]]
 [\\library
  ["[0]" /]])

(def: .public test
  Test
  (do random.monad
    [sample random.nat]
    (<| (_.covering /._)
        (all _.and
             (_.coverage [/.be]
               (n.= (++ sample)
                    (is (Identity Nat)
                        (/.be identity.comonad
                          [value (out sample)]
                          (out (++ value))))))
             ))))