Test creating book instance will pass test
Pass tests testing that Book class works
Add ShoppingBasket functionality to checkout an order of books
Add functionality to apply 5% discount to 2 unique books
Add functionality so discount is not applied for duplicate books
Add functionality to handle 5%, 10%, 20% and 25% discounts
Improve tests readability
Add test to check multiple discounts are handled where appropriate
Add new method and alter last test to use cheapest possible discount
Refactor shopping_basket and tidy up comments