public void ItAddDamageFee() { // Arrange var rentPeriod = new DateRange(DateTime.Now.Date, DateTime.Now.Date.AddDays(1)); var productsToRent = new List <Product> { new Product { Status = ProductStatus.Available, RentDailyPrice = 10, RentDailyLateFee = 1 } }; var renter = new Renter(); var rent = new Rent(rentPeriod, productsToRent, renter); // Act rent.AddDamageFee(5); // Assert Assert.Equal(5, rent.DamageFee); Assert.True(rent.WasProductDamaged); }