Updated the test system

test/permutations.test.js

@@ -0,0 +1,16 @@
+const expect = require('expect');
+const {permutations} = require('./_30s.js');
+
+test('permutations is a Function', () => {
+  expect(permutations).toBeInstanceOf(Function);
+});
+test('Generates all permutations of an array', () => {
+  expect(permutations([1, 33, 5])).toEqual([
+    [1, 33, 5],
+    [1, 5, 33],
+    [33, 1, 5],
+    [33, 5, 1],
+    [5, 1, 33],
+    [5, 33, 1]
+  ]);
+});