private void VerifyFlag(Func <TestData.FlagBuilder, TestData.FlagBuilder> configureFlag, string expectedProps)
        {
            var expectedJson = "{\"key\":\"flagkey\",\"version\":1," + expectedProps +
                               ",\"clientSide\":false,\"deleted\":false,\"prerequisites\":[],\"salt\":\"\"}";

            var td = TestData.DataSource();

            td.CreateDataSource(_context, _updates).Start();

            td.Update(configureFlag(_td.Flag("flagkey")));

            Assert.Equal(1, _updates.Upserts.Count);
            var up   = _updates.Upserts.Take();
            var json = LdValue.Parse(DataModel.Features.Serialize(up.Item));

            AssertHelpers.JsonEqual(LdValue.Parse(expectedJson), json);
        }