Updated the test system

test/serializeCookie.test.js

@@ -0,0 +1,9 @@
+const expect = require('expect');
+const {serializeCookie} = require('./_30s.js');
+
+test('serializeCookie is a Function', () => {
+  expect(serializeCookie).toBeInstanceOf(Function);
+});
+test('Serializes the cookie', () => {
+  expect(serializeCookie('foo', 'bar')).toBe('foo=bar');
+});