@Test
  public void shouldCreateAddressBookWithANewContact() {
    AddressBookBuilder addressBookbuilder = AddressBookBuilder.getAddressBookBuilder();
    ContactBuilder contactBuilder = ContactBuilder.getContactBuilder();
    Contact contact1 =
        contactBuilder.withName("Will").withNumber("0199999999").withNumber("0299999999").build();
    AddressBook book = addressBookbuilder.withName("Book 1").withContact(contact1).build();
    assertNotNull(book);
    assertEquals(1, book.getContacts().size());

    Contact contact2 =
        contactBuilder.withName("Bill").withNumber("0399999999").withNumber("0499999999").build();
    Set<Contact> contactSet = new HashSet<Contact>();
    contactSet.add(contact2);
    book = addressBookbuilder.withName("Book 1").withNewContactSet(contactSet).build();
    assertNotNull(book);
    assertEquals(1, book.getContacts().size());
  }
  @Test
  public void shouldCreateAddressBookWithContact() {
    AddressBookBuilder addressBookbuilder = AddressBookBuilder.getAddressBookBuilder();
    ContactBuilder contactBuilder = ContactBuilder.getContactBuilder();
    Contact contact1 =
        contactBuilder.withName("Will").withNumber("0199999999").withNumber("0299999999").build();
    AddressBook book = addressBookbuilder.withName("Book 1").withContact(contact1).build();

    assertNotNull(book);
    assertEquals(1, book.getContacts().size());

    Contact contact2 =
        contactBuilder.withName("Boby").withNumber("0199999999").withNumber("0299999999").build();
    book = addressBookbuilder.withContact(contact2).build();

    assertNotNull(book);
    assertEquals(2, book.getContacts().size());
  }