public void WhenCoinsAreInsertedAndReturnCoinsIsSelectedThenCoinValueGoesToCoinReturn()
        {
            vendingService.AcceptCoin("nickel");
            vendingService.AcceptCoin("dime");
            Assert.That(vendingService.GetDisplay(), Is.EqualTo("£0.15"));

            vendingService.ReturnCoins();
            Assert.That(vendingService.GetDisplay(), Is.EqualTo("INSERT COIN"));
            var expectedCoins = new[] { "nickel", "dime" };

            Assert.That(vendingService.EmptyCoinReturn(), Is.EquivalentTo(expectedCoins));
        }
        public void CustomerIsAbleToReturnCoinsAfterSelectingSoldOutProduct()
        {
            var vendingService = new VendingService();

            vendingService.AddStock(Item.Pepsi);
            vendingService.AcceptCoin("quarter");
            vendingService.AcceptCoin("quarter");
            vendingService.AcceptCoin("quarter");
            vendingService.AcceptCoin("quarter");
            Assert.That(vendingService.GetDisplay(), Is.EqualTo("£1.00"));

            vendingService.SelectProduct(Item.Coke);
            Assert.That(vendingService.GetDisplay(), Is.EqualTo("SOLD OUT"));
            Assert.That(vendingService.GetDisplay(), Is.EqualTo("£1.00"));

            vendingService.ReturnCoins();
            Assert.That(vendingService.EmptyCoinReturn(), Is.EquivalentTo(new[] { "quarter", "quarter", "quarter", "quarter" }));
        }