该is宏是核心clojure.test库。它返回其主体表达式的值,如果该表达式返回假值,则输出错误消息。
(defn square [x] (+ x x)) (require '[clojure.test :as t]) (t/is (= 0 (square 0))) ;;=> true (t/is (= 1 (square 1))) ;; ;; FAIL in () (foo.clj:1) ;; expected: (= 1 (square 1)) ;; actual: (not (= 1 2)) ;;=> false