public void TestMakeChange()
{
//arrange
Catering catering = new Catering(fa);
//act
catering.AddMoney("20");
//Assert
Assert.AreEqual("1 - Twenty", catering.MakeChange());
//act
catering.AddMoney("40");
//Assert
Assert.AreEqual("2 - Twenty", catering.MakeChange());
//act
catering.AddMoney("50");
//Assert
Assert.AreEqual("2 - Twenty, 1 - Ten", catering.MakeChange());
}