Project Euler #1

one.clj

(ns problems.one)

(defn- multiple-of [num x] (zero? (mod x num)))
(defn- multiples-of-three-and-five [x]
  (or (multiple-of 3 x)
      (multiple-of 5 x)))

(defn- real-numbers-below [x] (range 1 x))

(defn multiples-of-three-and-five-below [x]
  (filter multiples-of-three-and-five (real-numbers-below x)))

(defn sum-of-multiples [x]
  (reduce + (multiples-of-three-and-five-below x)))

(sum-of-multiples 10000)

one_test.clj

(ns problems.one-test
  (:require [clojure.test :refer :all]
            [problems.one :refer :all]))

(deftest multiples-of-n
  (testing "below 10 the multiples should be 3 5 6 and 9"
    (is (= (multiples-of-three-and-five-below 10), [3 5 6 9])))

  (testing "the sum of all multiples below 10 should be 23"
    (is (= (sum-of-multiples 10), 23)))

  ; SPOILERS!!!
  (testing "the sum of all multiples below 1000 should be something"
    (is (= (sum-of-multiples 1000), 233168)))
)