(require '[clojure.spec.alpha :as s]
         '[clojure.spec.test.alpha :as ta])

(defn add [x]
  (fn [y]
    (+ x y)))

(s/def ::num (s/double-in :infinite? false
                          :NaN? false))

(ta/check-fn add
  (s/fspec :args (s/cat :x ::num)
           :ret (s/fspec :args (s/cat :y ::num)
                         :ret ::num)
           :fn #(= (-> % :args :x) ((:ret %) 0))))