Add solution for greatest common divisor issue (#446)

* Add solution for greatest common divisor issue

* Fix typo

Co-authored-by: Vitaly <vtmilyakov@yandex.ru>

src/battle_asserts/issues/greatest_common_divisor.clj

@@ -0,0 +1,29 @@
+(ns battle-asserts.issues.greatest-common-divisor
+  (:require [clojure.test.check.generators :as gen]))
+
+(def level :easy)
+
+(def description "Create a function that calculates GCD (Greatest Common Divisor).")
+
+(def signature
+  {:input [{:argument-name "x" :type {:name "integer"}}
+           {:argument-name "y" :type {:name "integer"}}]
+   :output {:type {:name "integer"}}})
+
+(defn arguments-generator []
+  (gen/tuple (gen/choose 1 50) (gen/choose 1 50)))
+
+(def test-data
+  [{:arguments [8 24]
+    :expected 8}
+   {:arguments [8 26]
+    :expected 2}
+   {:arguments [42 56]
+    :expected 14}
+   {:arguments [15 50]
+    :expected 5}])
+
+(defn solution [x y]
+  (if (zero? y)
+    x
+    (recur y (mod x y))))

test/battle_asserts/issues/greatest_common_divisor_test.clj

@@ -0,0 +1,14 @@
+(ns battle-asserts.issues.greatest-common-divisor-test
+  (:require [clojure.test :refer :all]
+            [clojure.test.check.properties :as prop]
+            [clojure.test.check.clojure-test :as ct]
+            [test-helper :as h]
+            [battle-asserts.issues.greatest-common-divisor :as issue]))
+
+(ct/defspec spec-solution
+  20
+  (prop/for-all [v (issue/arguments-generator)]
+                (instance? Number (apply issue/solution v))))
+
+(deftest test-solution
+  (h/generate-tests issue/test-data issue/solution))