I got sidetracked

birthdays.clj

(defonce full-date-pattern (DateTimeFormatter/ofPattern "yyyy/MM/dd"))
(defonce birthday-pattern (DateTimeFormatter/ofPattern "MM/dd"))

(defn is-birthday? [day birthday]
  (string/ends-with?
    birthday
    (.format day birthday-pattern)))

(with-test
  #'is-birthday?
  (->>
    (repeatedly #(let [year (+ 1000 (rand-int 1020))
                       month (format "%02d" (inc (rand-int 12)))
                       day (inc (rand-int 31))
                       day (if (and (= month 2) (> day 28)) 28 day)
                       other-day (if (= (rand-int 2) 0) day (inc (rand-int 31)))
                       day (format "%02d" day)
                       other-day (format "%02d" other-day)]
                   (vector
                     [year month day]
                     [year month other-day])))
    (take 1000)
    (map (fn [[[year1 month1 day1] [year2 month2 day2]]]
           [(str year1 "/" month1 "/" day1)
            (str year2 "/" month2 "/" day2)]))
    (map (fn [[d1 d2]]
           (let [date1 (LocalDate/parse d1 full-date-pattern)
                 date2 (LocalDate/parse d2 full-date-pattern)]
             [date1 (.format date2 birthday-pattern) (= 0 (compare date1 date2))])))
    (mapv
      (fn [[day bday expected]]
        (let [day-str (.format day birthday-pattern)
              actual  (is-birthday? day bday)]
          (testing (str day-str " should be" (when expected " be " " not be ") "considered to be the same day as " bday)
            (if expected
              (is actual)
              (is (not actual)))))))))

(test-ns *ns*)