public void ExactAmountTendered()
{
VendingMachine machine = new BacktrackingGreedyVendingMachine();
machine.Add
(
Change.OnePence(100),
Change.FivePence(50),
Change.TenPence(50)
);
int totalValueMachineBeforeVend = machine.Balance.TotalValue();
VendingResult result = machine.Vend(60, Change.FiftyPence(1), Change.TenPence(1));
Assert.IsNotNull(result);
Assert.IsTrue(result.Success);
Assert.IsNotNull(result.Change);
// We should have no change...
Assert.AreEqual(result.Change.TotalValue(), 0);
// ...and the machine should have 60 more than before then vend
Assert.AreEqual(machine.Balance.TotalValue(), 60 + totalValueMachineBeforeVend);
}
public void CanGiveChange()
{
VendingMachine machine = new BacktrackingGreedyVendingMachine();
machine.Add
(
Change.OnePence(100),
Change.FivePence(50),
Change.TenPence(50)
);
int totalValueMachineBeforeVend = machine.Balance.TotalValue();
VendingResult result = machine.Vend(25, Change.TwentyPence(2));
Assert.IsNotNull(result);
Assert.IsTrue(result.Success);
Assert.IsNotNull(result.Change);
// We should have 15p in change...
Assert.AreEqual(result.Change.TotalValue(), 15);
// ...and the machine should have 25p more than before then vend
Assert.AreEqual(machine.Balance.TotalValue(), 25 + totalValueMachineBeforeVend);
}
public void CannotGiveChange()
{
VendingMachine machine = new BacktrackingGreedyVendingMachine();
machine.Add
(
Change.TwoPence(3),
Change.FivePence(1),
Change.TenPence(1)
);
int totalValueMachineBeforeVend = machine.Balance.TotalValue();
// The change here is 3p, which we don't have
VendingResult result = machine.Vend(17, Change.TenPence(2));
Assert.IsNotNull(result);
Assert.IsTrue(result.Failed);
// We shouldn't have any change...
Assert.AreEqual(result.Change.TotalValue(), 0);
// ...and the machine should have the same balance as before the vend
Assert.AreEqual(machine.Balance.TotalValue(), totalValueMachineBeforeVend);
}
public void GiveChangeAfterRecursiveAdjustment_1()
{
VendingMachine machine = new BacktrackingGreedyVendingMachine();
machine.Add
(
Change.TwoPence(3),
Change.FivePence(1),
Change.TenPence(10),
Change.FiftyPence(2)
);
int totalValueMachineBeforeVend = machine.Balance.TotalValue();
// The change here is 6p and we've got the right coins, 3 x 2p
// A pure greedy approach will fail here as it will take the 5p but not find a 1p
// However, the backtracking greedy approach will ignore the 5p and try with the remaining coins
VendingResult result = machine.Vend(14, Change.TenPence(2));
Assert.IsNotNull(result);
Assert.IsTrue(result.Success);
// We should have 6p change...
Assert.AreEqual(result.Change.TotalValue(), 6);
// ...and the machine should have 14p more than before then vend
Assert.AreEqual(machine.Balance.TotalValue(), 14 + totalValueMachineBeforeVend);
}
public void GiveChangeAfterRecursiveAdjustment_2()
{
VendingMachine machine = new BacktrackingGreedyVendingMachine();
machine.Add
(
Change.TwoPence(3),
Change.FivePence(1),
Change.TwentyPence(3),
Change.FiftyPence(1)
);
// NOTE: The backtracking machine removes coins in its balance that
// are greater than the change amount. In this scenerio it won't remove anything
int totalValueMachineBeforeVend = machine.Balance.TotalValue();
// The change here is 66p and we've got the right coins, 3 x 20p and 3 x 2p
// A pure greedy approach will fail here as it will take the 50p but not be able to make up the 16p
// However, the backtracking greedy approach will ignore the 50p and try with the remaining coins
VendingResult result = machine.Vend(34, Change.OnePound(1));
Assert.IsNotNull(result);
Assert.IsTrue(result.Success);
// We should have 66p change...
Assert.AreEqual(result.Change.TotalValue(), 66);
// ...and the machine should have 34p more than before then vend
Assert.AreEqual(machine.Balance.TotalValue(), 34 + totalValueMachineBeforeVend);
}
