public void Add_inserts_new_entity_in_to_the_collection()
{
// arrange
var entity = GenerateDomainObject();
// act
_repository.Add(entity);
_repository.SaveChanges();
// assert
var newEntity = _client.Set <T>().Find(x => x.Id == entity.Id).FirstOrDefault();
Assert.IsType <T>(newEntity);
}