public void EmptySetsQuantityToZero()
{
VendingMachineViewModel vendingMachineViewModel = new VendingMachineViewModel();
vendingMachineViewModel.Refill();
vendingMachineViewModel.Empty();
Assert.Multiple(() =>
{
Assert.AreEqual(0, vendingMachineViewModel.Items[0].Quantity);
Assert.AreEqual(0, vendingMachineViewModel.Items[1].Quantity);
Assert.AreEqual(0, vendingMachineViewModel.Items[2].Quantity);
Assert.AreEqual(0, vendingMachineViewModel.Items[3].Quantity);
});
}