Add tests for reduce (#81)

* Add tests for reduce

* Add tests for edge-cases described in the docstring

Author: cddr

test/clojure/core_test/reduce.cljc

@@ -0,0 +1,97 @@
+(ns clojure.core-test.reduce
+  (:require
+   [clojure.test :as t :refer [deftest testing is are]]
+   [clojure.core-test.portability #?(:cljs :refer-macros :default :refer)  [when-var-exists]])
+  #?(:clj (:import (clojure.lang IReduce))))
+
+(def interop
+  {:int-new (fn [x]
+              (#?(:clj Integer.
+                  :cljs js/Number.) x))
+
+   :Integer #?(:clj Integer/TYPE
+               :cljs js/Number)
+
+   :Long #?(:clj Long/TYPE
+            :cljs js/Number)
+
+   :Float #?(:clj Long/TYPE
+             :cljs js/Number)
+
+   :Double #?(:clj Double/TYPE
+              :cljs js/Number)
+
+   :Boolean #?(:clj Boolean/TYPE
+               :cljs js/Boolean)})
+
+
+(when-var-exists clojure.core/reduce
+  (deftest test-reduce
+    (testing "common"
+      (is (nil? (reduce nil nil nil)))
+      (is (thrown? #?(:clj Exception
+                      :cljs js/Error) (reduce nil nil)))
+      (is (= 6 (reduce + 0 [1 2 3]))))
+
+    (testing "val is not supplied"
+      (is (= 3 (reduce (fn [a b]
+                         (+ a b))
+                       [1 2])))
+
+      (testing "empty coll"
+        (is (= 1 (reduce (fn [] 1) []))))
+
+      (testing "coll with 1 item"
+        (is (= 1 (reduce (fn []
+                           (is false)
+                           (throw (ex-info "should not get here" {})))
+                         [1])))))
+
+    (testing "val is supplied, empty coll"
+      (is (= 1 (reduce (fn []
+                           (is false)
+                         (throw (ex-info "should not get here" {})))
+                       1
+                       []))))
+
+    (testing "reduction by type"
+      (let [int-new (interop :int-new)
+            char-new (interop :char-new)
+            byte-new (interop :byte-new)
+            arange (range 1 100) ;; enough to cross nodes
+            avec (into [] arange)
+            alist (into () arange)
+            obj-array (into-array arange)
+            int-array (into-array (:Integer interop) (map #(int-new (int %)) arange))
+            long-array (into-array (:Long interop) arange)
+            float-array (into-array (:Float interop) arange)
+            double-array (into-array (:Double interop) arange)
+            all-true (into-array (:Boolean interop) (repeat 10 true))]
+
+        (testing "val is not supplied"
+          (is (== 4950
+                  (reduce + arange)
+                  (reduce + avec)
+                  #?(:clj (.reduce ^IReduce avec +))
+                  (reduce + alist)
+                  (reduce + obj-array)
+                  (reduce + int-array)
+                  (reduce + long-array)
+                  (reduce + float-array)
+                  (reduce + double-array))))
+
+        (testing "val is supplied"
+          (is (== 4951
+                  (reduce + 1 arange)
+                  (reduce + 1 avec)
+                  #?(:clj (.reduce ^IReduce avec + 1))
+                  (reduce + 1 alist)
+                  (reduce + 1 obj-array)
+                  (reduce + 1 int-array)
+                  (reduce + 1 long-array)
+                  (reduce + 1 float-array)
+                  (reduce + 1 double-array))))
+
+        (is (= true
+               (reduce #(and %1 %2) all-true)
+               (reduce #(and %1 %2) true all-true)))))))