Use Clojure.Spec for Functions

(defn int-to-digits
  (str number))

Function specifications (or specs) are defined with s/fdef.

(s/fdef int-to-digits
  :args (s/cat :number int?))

The function’s argument names and the keywords in the :args spec don’t have to match, it’s position based.

The instrument function can be now used to assert the :args spec:

(stest/instrument `int-to-digits)

The :ret spec can be used to provide a specification for the return value:

(s/fdef number-to-digits
  :args (s/cat :number int?)
  :ret (s/coll-of char? :kind set? :min-count 1))

The :ret spec can be checked with the check function.

(stest/check `number-to-digits)