public void DataRepositoryAddClientTest()
        {
            Assert.AreEqual(3, repository.GetClientsNumber());

            repository.AddClient(new Data.Client(4, "Mateusz", "Owczarek", 22));
            repository.AddClient(new Data.Client(5, "Maciej", "Kopa", 16));
            repository.AddClient(new Data.Client(6, "Monika", "Roksa", 23));

            Assert.AreEqual(6, repository.GetClientsNumber());
        }
 public int GetClientsNumber()
 {
     return(repository.GetClientsNumber());
 }