Hamcrest

(defmatcher is-zero? []
            :match? (= item 0)
            :match! "a zero"
            :no-match! (.format "was a value of {0}" item))

(assert-that 0 (is-zero?))

(attribute-matcher item-with-length?
                   len =
                   "an item with length {0}"
                   "was an item with length {0}")

(assert-that "foo" (is- (item-with-length? 3)))