Clojure implementation of the bowling kata

core.clj

(ns bowling.core)

(defn spare? [rolls]
  (= 10 (reduce + (take 2 rolls))))

(defn strike? [rolls]
  (= 10 (first rolls)))

(defn take-how-many [rolls]
  (if (or (spare? rolls) (strike? rolls)) 3 2))

(defn drop-how-many [rolls]
  (if (strike? rolls) 1 2))

(defn make-frames [rolls]
  (let [must-take (take-how-many rolls)
        must-drop (drop-how-many rolls)]
    (lazy-seq
     (cons
      (take must-take rolls)
      (make-frames (drop must-drop rolls))))))

(defn make-game [rolls]
  (take 10 (make-frames rolls)))

(defn frame-score [frame]
  (reduce + frame))

(defn game-score [rolls]
  (reduce + (map frame-score (make-game rolls))))

core_test.clj

(ns bowling.core-test
  (:use clojure.test
        bowling.core))

(deftest spare?-test
  (testing "We know what a spare is"
    (is (= true (spare? [1 9])))
    (is (= false (spare? [1 1])))
    (is (= false (spare? [10 1])))))

(deftest strike?-test
  (testing "We know what a strike is"
    (is (= true (strike? [10 1 9])))
    (is (= false (strike? [1 9 10])))))

(deftest take-how-many-test
  (testing "We take two for a simple game"
    (is (= 2 (take-how-many [1 2 1]))))
  (testing "We take three from a spare game"
    (is (= 3 (take-how-many [1 9 1]))))
  (testing "We take three for a strike"
    (is (= 3 (take-how-many [10 2 1])))))

(deftest drop-how-many-test
  (testing "We drop two for a simple game"
    (is (= 2 (drop-how-many [1 2 1]))))
  (testing "We drop 2 from a spare game"
    (is (= 2 (drop-how-many [1 9 1]))))
  (testing "We drop one for a strike"
    (is (= 1 (drop-how-many [10 2 1])))))

(deftest make-frames-test
  (testing "Returns simple frame for simple game"
    (is (= '((1 1)) (take 1 (make-frames [1 1 1 1])))))
  (testing "Returns correct frame for game with spare"
    (is (= '((1 9 1)) (take 1 (make-frames [1 9 1 1])))))
  (testing "Returns correct frame for game with strikes"
    (is (= '((10 10 10)) (take 1 (make-frames [10 10 10]))))))

(deftest make-game-test
  (testing "Returns the correct game for a simple game"
    (is (= '((1 1) (1 1) (1 1) (1 1) (1 1) (1 1) (1 1) (1 1) (1 1) (1 1))
           (make-game (repeat 20 1)))))
    (testing "Returns the correct game for a mixed game"
      (is (= '((1 9 1) (1 2) (10 1 1) (1 1) (1 1) (1 1) (1 1) (1 1) (1 1) (1 1))
             (make-game (concat [1 9 1 2 10] (repeat 14 1)))))))

(deftest frame-score-test
  (testing "We can calculate the score of a frame"
    (is (= 2 (frame-score [1 1])))
    (is (= 11 (frame-score [1 9 1])))
    (is (= 30 (frame-score [10 10 10])))))

(deftest scoring-tests
  (testing "A gutter balls"
    (is (= 0 (game-score (repeat 20 0)))))
  (testing "All rolls are of one pin"
    (is (= 20 (game-score (repeat 20 1)))))
  (testing "Has a spare in the first round"
    (is (= 29 (game-score (concat [1 9] (repeat 18 1))))))
  (testing "Perfect game"
    (is (= 300 (game-score (repeat 13 10)))))
  (testing "Random game"
    (is (= 145 (game-score [1 9 2 4 10 10 10 7 1 2 8 7 0 0 0 10 1 9])))))