vendingMachineKata.txt

THE VENDING MACHINE KATA 
    with many thanks to Guy Royce https://github.com/guyroyse/vending-machine-kata

In this exercise you will build the brains of a vending machine. 
It will accept money, make change, maintain inventory, and dispense products. 
All the things that you might expect a vending machine to accomplish.

The point of this kata to to provide a larger than trivial exercise that can be 
used to practice TDD. A significant portion of the effort will be in determining 
what tests should be written and, more importantly, written next.

FEATURES:

ACCEPT COINS
    As a vendor
    I want a vending machine that accepts coins
    So that I can collect money from the customer


    The vending machine will accept valid coins (nickels, dimes, and quarters) 
    and reject invalid ones (pennies). When a valid coin is inserted 
    the amount of the coin will be added to the current amount 
    and the display will be updated. When there are no coins inserted, 
    the machine displays INSERT COIN. Rejected coins are placed in the coin return.

    NOTE: The temptation here will be to create Coin objects that know their value. 
    However, this is not how a real vending machine works. Instead, it identifies 
    coins by their weight and size and then assigns a value to what was inserted. 
    You will need to do something similar. This can be simulated using strings, 
    constants, enums, symbols, or something of that nature.


SELECT A PRODUCT
    As a vendor
    I want customers to select products
    So that I can give them an incentive to put money in the machine

    There are three products: cola for $1.00, chips for $0.50, and 
    candy for $0.65. When the respective button is pressed 
    and enough money has been inserted, the product is dispensed 
    and the machine displays THANK YOU. 
    If the display is checked again, it will display INSERT COIN 
    and the current amount will be set to $0.00. 
    If there is not enough money inserted then the machine displays PRICE 
    and the price of the item and subsequent checks of the 
    display will display either INSERT COIN or the current amount as appropriate.


MAKE CHANGE
    As a vendor
    I want customers to receive correct change
    So that they will use the vending machine again

    When a product is selected that costs less than the amount of 
    money in the machine, then the remaining amount is placed in the coin return.


RETURN COINS
    As a customer
    I want to have my money returned
    So that I can change my mind about buying stuff from the vending machine

    When the return coins button is pressed, the money the customer has placed 
    in the machine is returned and the display shows INSERT COIN.


SOLD OUT
    As a customer
    I want to be told when the item I have selected is not available
    So that I can select another item

    When the item selected by the customer is out of stock, 
    the machine displays SOLD OUT. If the display is checked again, 
    it will display the amount of money remaining in the machine 
    or INSERT COIN if there is no money in the machine.


EXACT CHANGE ONLY
    As a customer
    I want to be told when exact change is required
    So that I can determine if I can buy something with the money I have 
    before inserting it

    When the machine is not able to make change with the money in the machine 
    for any of the items that it sells, it will display EXACT CHANGE ONLY 
    instead of INSERT COIN.
    
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