Checkout Kata

Implement the code for a supermarket checkout that calculates the total price of a number of items. In a normal supermarket, things are identified using Stock Keeping Units, or SKUs. In our store, we’ll use individual letters of the alphabet (A, B, C, and so on as the SKUs). Our goods are priced individually. In addition, some items are multi-priced: buy n of them, and they’ll cost you y. For example, item ‘A’ might cost 50 pence individually, but this week we have a special offer: buy three ‘A’s and they’ll cost you £1.30. In fact this week’s prices are:

Item	Unit Price	Special Price
A	50	3 for 130
B	30	2 for 45
C	20
D	15

Our checkout accepts items in any order, so that if we scan a B, an A, and another B, we’ll recognise the two B’s and price them at 45 (for a total price so far of 95). Because the pricing changes frequently, we need to be able to pass in a set of pricing rules handling a checkout transaction.

To run the test in the console, just type:

sbt test

If you want run an interactive session, just type:

sbt run