test(contains): add contains test

Author: djcsdy

index.test.ts

@@ -1,5 +1,6 @@
 import test from "ava";
 import {
+    contains,
     dropWhile,
     empty,
     exclude,
@@ -185,6 +186,11 @@ test("foldMap", t => {
     );
 });
 
+test("contains", t => {
+    t.true(contains([1, 2, 3], 1));
+    t.false(contains([1, 2, 3], 0));
+});
+
 test("findIndex", t => {
     t.is(
         findIndex([1, 2, 3, 4, 3, 2, 1], n => n >= 3),