private void AssertDiscountRate(int numberOfBooks, int expectedDiscountPercentage)
{
var rateCard = new DiscountRateCard();
var discount = rateCard.CalculateDiscountRate(numberOfBooks);
Assert.That(discount, Is.EqualTo(expectedDiscountPercentage));
Debug.WriteLine("{0} books gives {1}% discount", numberOfBooks, expectedDiscountPercentage);
}
public void PassingDiscountRateCardAnInvalidNumberOfBooksCausesException()
{
var rateCard = new DiscountRateCard();
Assert.Throws<ArgumentException>(() => rateCard.CalculateDiscountRate(8));
}