anchor.diff:        "emails": [],
         "phones": [],
         "postalAddresses": [],
  -      "avatar": null
  +      "avatar": null,
  +      "birthday": null
       });
     });
   }
  
positive.code:             'country': null
            }
          ],
          'avatar': null
        },
      ),
    ]);
  
negative.code:   });
  
    test('should get contacts', () async {
      final contacts = await ContactsService.getContacts();
      expect(contacts.length, 2);
      expect(contacts, everyElement(isInstanceOf<Contact>()));
      expect(contacts.toList()[0].givenName, 'givenName1');
      expect(contacts.toList()[1].postalAddresses.toList()[0].label, 'label');
      expect(contacts.toList()[1].emails.toList()[0].label, 'label');
      expect(contacts.toList()[1].birthday, DateTime(1994, 2, 1));
    });
  
    test('should add contact', () async {
  