public void ReturnsChange(decimal purchasePrice, decimal expectedChange)
        {
            var system = new VendingSystem(products, bankedCoins);

            system.TotalValue = 1.5m;

            var change = system.MakeChange(purchasePrice);

            Assert.Equal(expectedChange, change);
        }
        public void ReturnsNoChange(decimal purchasePrice, decimal expectedChange)
        {
            bankedCoins = new List <Coin>
            {
                new Coin(5.000m, 21.21m),
                new Coin(5.000m, 21.21m),
            };

            var system = new VendingSystem(products, bankedCoins);

            system.TotalValue = 1.5m;

            var change = system.MakeChange(purchasePrice);

            Assert.Equal(expectedChange, change);
        }