public void UsersFieldsTest()
        {
            // get test
            Assert.That(UsersFields.Nickname.ToString(), Is.EqualTo("nickname"));
            Assert.That(UsersFields.Domain.ToString(), Is.EqualTo("domain"));
            Assert.That(UsersFields.Sex.ToString(), Is.EqualTo("sex"));
            Assert.That(UsersFields.BirthDate.ToString(), Is.EqualTo("bdate"));
            Assert.That(UsersFields.City.ToString(), Is.EqualTo("city"));
            Assert.That(UsersFields.Country.ToString(), Is.EqualTo("country"));
            Assert.That(UsersFields.Timezone.ToString(), Is.EqualTo("timezone"));
            Assert.That(UsersFields.Photo50.ToString(), Is.EqualTo("photo_50"));
            Assert.That(UsersFields.Photo100.ToString(), Is.EqualTo("photo_100"));
            Assert.That(UsersFields.Photo200Orig.ToString(), Is.EqualTo("photo_200_orig"));
            Assert.That(UsersFields.Photo200.ToString(), Is.EqualTo("photo_200"));
            Assert.That(UsersFields.Photo400Orig.ToString(), Is.EqualTo("photo_400_orig"));
            Assert.That(UsersFields.PhotoMax.ToString(), Is.EqualTo("photo_max"));
            Assert.That(UsersFields.PhotoMaxOrig.ToString(), Is.EqualTo("photo_max_orig"));
            Assert.That(UsersFields.HasMobile.ToString(), Is.EqualTo("has_mobile"));
            Assert.That(UsersFields.Contacts.ToString(), Is.EqualTo("contacts"));
            Assert.That(UsersFields.Education.ToString(), Is.EqualTo("education"));
            Assert.That(UsersFields.Online.ToString(), Is.EqualTo("online"));
            Assert.That(UsersFields.OnlineMobile.ToString(), Is.EqualTo("online_mobile"));
            Assert.That(UsersFields.FriendLists.ToString(), Is.EqualTo("lists"));
            Assert.That(UsersFields.Relation.ToString(), Is.EqualTo("relation"));
            Assert.That(UsersFields.LastSeen.ToString(), Is.EqualTo("last_seen"));
            Assert.That(UsersFields.Status.ToString(), Is.EqualTo("status"));

            Assert.That(UsersFields.CanWritePrivateMessage.ToString()
                        , Is.EqualTo("can_write_private_message"));

            Assert.That(UsersFields.CanSeeAllPosts.ToString(), Is.EqualTo("can_see_all_posts"));
            Assert.That(UsersFields.CanPost.ToString(), Is.EqualTo("can_post"));
            Assert.That(UsersFields.Universities.ToString(), Is.EqualTo("universities"));
            Assert.That(UsersFields.Connections.ToString(), Is.EqualTo("connections"));
            Assert.That(UsersFields.Site.ToString(), Is.EqualTo("site"));
            Assert.That(UsersFields.Schools.ToString(), Is.EqualTo("schools"));
            Assert.That(UsersFields.CanSeeAudio.ToString(), Is.EqualTo("can_see_audio"));
            Assert.That(UsersFields.CommonCount.ToString(), Is.EqualTo("common_count"));
            Assert.That(UsersFields.Relatives.ToString(), Is.EqualTo("relatives"));
            Assert.That(UsersFields.Counters.ToString(), Is.EqualTo("counters"));

            Assert.That(UsersFields.All.ToString()
                        , Is.EqualTo("bdate,can_post,can_see_all_posts,can_see_audio,can_write_private_message,city,common_count,connections,contacts,counters,country,domain,education,has_mobile,last_seen,lists,nickname,online,online_mobile,photo_100,photo_200,photo_200_orig,photo_400_orig,photo_50,photo_max,photo_max_orig,relation,relatives,schools,sex,site,status,timezone,universities"));

            // parse test
            Assert.That(UsersFields.FromJsonString("nickname"), Is.EqualTo(UsersFields.Nickname));
            Assert.That(UsersFields.FromJsonString("domain"), Is.EqualTo(UsersFields.Domain));
            Assert.That(UsersFields.FromJsonString("sex"), Is.EqualTo(UsersFields.Sex));
            Assert.That(UsersFields.FromJsonString("bdate"), Is.EqualTo(UsersFields.BirthDate));
            Assert.That(UsersFields.FromJsonString("city"), Is.EqualTo(UsersFields.City));
            Assert.That(UsersFields.FromJsonString("country"), Is.EqualTo(UsersFields.Country));
            Assert.That(UsersFields.FromJsonString("timezone"), Is.EqualTo(UsersFields.Timezone));
            Assert.That(UsersFields.FromJsonString("photo_50"), Is.EqualTo(UsersFields.Photo50));
            Assert.That(UsersFields.FromJsonString("photo_100"), Is.EqualTo(UsersFields.Photo100));

            Assert.That(UsersFields.FromJsonString("photo_200_orig")
                        , Is.EqualTo(UsersFields.Photo200Orig));

            Assert.That(UsersFields.FromJsonString("photo_200"), Is.EqualTo(UsersFields.Photo200));

            Assert.That(UsersFields.FromJsonString("photo_400_orig")
                        , Is.EqualTo(UsersFields.Photo400Orig));

            Assert.That(UsersFields.FromJsonString("photo_max"), Is.EqualTo(UsersFields.PhotoMax));

            Assert.That(UsersFields.FromJsonString("photo_max_orig")
                        , Is.EqualTo(UsersFields.PhotoMaxOrig));

            Assert.That(UsersFields.FromJsonString("has_mobile"), Is.EqualTo(UsersFields.HasMobile));
            Assert.That(UsersFields.FromJsonString("contacts"), Is.EqualTo(UsersFields.Contacts));
            Assert.That(UsersFields.FromJsonString("education"), Is.EqualTo(UsersFields.Education));
            Assert.That(UsersFields.FromJsonString("online"), Is.EqualTo(UsersFields.Online));

            Assert.That(UsersFields.FromJsonString("online_mobile")
                        , Is.EqualTo(UsersFields.OnlineMobile));

            Assert.That(UsersFields.FromJsonString("lists"), Is.EqualTo(UsersFields.FriendLists));
            Assert.That(UsersFields.FromJsonString("relation"), Is.EqualTo(UsersFields.Relation));
            Assert.That(UsersFields.FromJsonString("last_seen"), Is.EqualTo(UsersFields.LastSeen));
            Assert.That(UsersFields.FromJsonString("status"), Is.EqualTo(UsersFields.Status));

            Assert.That(UsersFields.FromJsonString("can_write_private_message")
                        , Is.EqualTo(UsersFields.CanWritePrivateMessage));

            Assert.That(UsersFields.FromJsonString("can_see_all_posts")
                        , Is.EqualTo(UsersFields.CanSeeAllPosts));

            Assert.That(UsersFields.FromJsonString("can_post"), Is.EqualTo(UsersFields.CanPost));

            Assert.That(UsersFields.FromJsonString("universities")
                        , Is.EqualTo(UsersFields.Universities));

            Assert.That(UsersFields.FromJsonString("connections"), Is.EqualTo(UsersFields.Connections));
            Assert.That(UsersFields.FromJsonString("site"), Is.EqualTo(UsersFields.Site));
            Assert.That(UsersFields.FromJsonString("schools"), Is.EqualTo(UsersFields.Schools));

            Assert.That(UsersFields.FromJsonString("can_see_audio")
                        , Is.EqualTo(UsersFields.CanSeeAudio));

            Assert.That(UsersFields.FromJsonString("common_count"), Is.EqualTo(UsersFields.CommonCount));
            Assert.That(UsersFields.FromJsonString("relatives"), Is.EqualTo(UsersFields.Relatives));
            Assert.That(UsersFields.FromJsonString("counters"), Is.EqualTo(UsersFields.Counters));

            Assert.That(UsersFields.FromJsonString("nickname,domain,sex,bdate,city,country,timezone,photo_50,photo_100,photo_200_orig,photo_200,photo_400_orig,photo_max,photo_max_orig,has_mobile,contacts,education,online,online_mobile,lists,relation,last_seen,status,can_write_private_message,can_see_all_posts,can_post,universities,connections,site,schools,can_see_audio,common_count,relatives,counters")
                        , Is.EqualTo(UsersFields.All));
        }