checking if fns are valid

deps.edn

{:paths ["resources" "src"]
 :deps {org.clojure/clojure {:mvn/version "RELEASE"}
        org.clojure/test.check {:mvn/version "RELEASE"}}
 :aliases
 {:test {:extra-paths ["test"]
         :extra-deps {org.clojure/test.check {:mvn/version "RELEASE"}}}
  :runner
  {:extra-deps {com.cognitect/test-runner
                {:git/url "https://github.com/cognitect-labs/test-runner"
                 :sha "76568540e7f40268ad2b646110f237a60295fa3c"}}
   :main-opts ["-m" "cognitect.test-runner"
               "-d" "test"]}}}

speculative.clj

(ns speculative
  (:require [clojure.spec.alpha :as s]
            [clojure.spec.test.alpha :as stest]))

;; This doesn't work all that well because it seems like
;; we use generative testing to verify that a higher order fn
;; satisfies the spec

(s/def ::reducing-fn (s/fspec :args (s/cat :accumulator any? :elem any?)))

(s/valid? ::reducing-fn (fn [x y]) ;; takes forever and ends with a out of heap memory