Capture domain knowledge once in specs, instead of burying it in tests

specs_over_tests.clj

;; compare to https://gist.github.com/lensgolda/13e549476fb65d3b8c2d71ca59b15937#file-test-clj

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

;; general domain knowledge, not buried in a test
(s/def ::info (s/keys :req-un [::name]))
(s/def ::items (s/coll-of pos-int?))
(s/def ::active boolean?)

;; knowledge specific to this test data
(s/def ::this-order (s/and (s/keys :req-un [::info ::active ::items])
                           #(= 3 (count (:items %)))))

;; successful test
(s/explain ::this-order
           {:info {:name "Lens"}
            :items [1 2 3]
            :active false})

;; failing test
(s/explain ::this-order
           {:info {}
            :items [1 2 3]
            :active false})