Make some methods private
Refactor: Change Customer class internal structure
Customer holds a Bill object instead of a list of purchases
Balance is no longer keept in a instance variable
Balance is calculated substracting total amount of payments from total amount of purchases
Extract method Purchases#set_bill
Refactor: Add parameter new_purchases to Bill#update method
Extract classes to it's own file
Remove unused method
Extract bill formatting logic to BillFormatter role
Remove unused code
Refactor: Remove WineCategories class
Rename WineCategory to WinePriceCode'
Extract module wine price codes'
Extract module wine price codes'
Remove TODO comment'
Refactor: Move all classes to WineStore module
Extract module CollectionWrapper
Refactor Payments to use CollectionWrapper