public void TotalCostTest1()
        {
            Rental rental = new Rental
            {
                RentedBike = new Bike
                {
                    FirstHourPrice      = 3,
                    AdditionalHourPrice = 5
                },
                RentalBegin = new DateTime(2018, 2, 14, 8, 15, 0),
                RentalEnd   = new DateTime(2018, 2, 14, 10, 30, 0)
            };

            var total = rc.CalculateTotalCost(rental);

            Assert.AreEqual(13, total);
        }