Summary

This is a code example that showcase my ability to solve real life problems, achiving a flexible, maintainable OOP solution by applying best practices such us TDD, Refactoring, Design-Patterns.
I encourage you to follow the commit's history so you can see how I guided the solution by tests, and after having a good test suite I started refactoring.

The problem

Given a supermarket which sell only three products:

+--------------|--------------|---------+
| Product Code |     Name     |  Price  |
+--------------|--------------|---------+
|     FR1      |   Fruit tea  |  $3.11  |
|     AP1      |   Apple      |  $5.00  |
|     CF1      |   Coffee     | $11.23  |
+--------------|--------------|---------+

The owner is a big fan of buy-one-get-one-free offers and of fruit tea. He wants us to add a rule to do this.

Also he likes low prices and wants people buying apple to get a price discount for bulk purchases. If you buy 3 or more apples, the price should drop to $4.50. Our check-out can scan items in any order, and it needs to be flexible regarding our pricing rules.

The interface to our checkout looks like this:

co = Checkout.new(pricing_rules)
co.scan(item)
co.scan(item)
price = co.total

Implement a checkout system that fulfils these requirements in Ruby.

Here are some test data:

Basket: FR1, AP1, FR1, CF1
Total price expected: $22.25
Basket: FR1, FR1
Total price expected: $3.11
Basket: AP1, AP1, FR1, AP1
Total price expected: $16.61

The solution

This repository implements a solution to the previous problem.
If you follow the commits you can see how it was built.
In particular, you can see the usage of TDD, Refactoring and Design-Patterns applied.