public ActionResult DeleteContact(string id, string username)
        {
            var addressBook = new RealAddressBook(username);

            addressBook.Delete(id);

            return RedirectToAction("DisplayAddressBook");
        }
        public void ShouldDeleteContactFromAddressBook()
        {
            const string username = "******";
            var addressBook = new RealAddressBook(username);

            var random = new Random();

            var firstName = "Amanda" + random.Next();
            var surname = "Jones" + random.Next();
            var telephoneNumber = "01724 567892" + random.Next();

            var customer = new Contact(firstName, surname, telephoneNumber);

            var contact = addressBook.Save(customer, username);

            var id = contact.Id.ToString();

            addressBook.Delete(id);

            var expectedResult = addressBook.Read(contact.Id);

            Assert.That(expectedResult, Is.EqualTo(null));
        }