public void TestForDuplicateReservation()
        {
            var repository  = new ReservationRepository(_context);
            var schedule    = repository.GetActiveSchedulesForTrain(1).First();
            var reservation = new Reservation {
                ReservationId = 2, Schedule = schedule, Passenger = "Phil Marlowe"
            };

            repository.AddReservation(reservation);
            repository.SaveChanges();
        }