Instructions

Your task is to define a shopping cart for a corner shop. The cart should keep track of the list of items added, and correctly calculate the price.

Items are added to the basket using stock-keeping unit (SKU) codes. The items in the shop are:

Name	Price	SKU
Potatoes	10.00	STAPOT
Rice	30.00	STARIC
Coffee	14.99	STACOF
Newspaper	2.99	MEDNEW

You need to define a ShoppingCart class, with three public methods:

• add: Takes a SKU and adds it to the cart. The SKU is a Symbol comprised of the first three uppercase letters of the product type + the first three uppercase letters of the product name.
• total_amount: The value of the items in the cart as a number with two decimal places (e.g. 3.99).
• items_list: A list of the names of the items in the cart, ordered alphabetically, with no duplicates, separated by a comma and a space.

For example:

shopping_cart = ShoppingCart.new
shopping_cart.add(:STAPOT)
shopping_cart.add(:STARIC)

shopping_cart.total_amount
// Returns: 40.00

shopping_cart.items_list
// Returns: "Potatoes, Rice"

Debugging

When a test fails, a message is displayed describing what went wrong and for which input. You can also use the fact that any console output will be shown too. You can write to the console using:

debug("Debug message")