Updated the test system

test/forEachRight.test.js

@@ -0,0 +1,11 @@
+const expect = require('expect');
+const {forEachRight} = require('./_30s.js');
+
+test('forEachRight is a Function', () => {
+  expect(forEachRight).toBeInstanceOf(Function);
+});
+let output = '';
+forEachRight([1, 2, 3, 4], val => (output += val));
+test('Iterates over the array in reverse', () => {
+  expect(output).toBe('4321');
+});