RubyTDD: small TDD Ruby exercise

This is a simple and small exercise on how to use TDD on Ruby.

Requirements

Technical Requirements:

• Use Ruby (no RoR).
• Develop using TDD methodology (Test Driven Development).
• Use Git as SCM:
  • After each test do a commit.
  • Although there is no need to use Github it would be better. Local repository sent by email is an option too.
• No need to use a DB.

Functional Requirements

Product code	Name	Price
GR1	Green tea	£3.11
SR1	Strawberries	£5.00
CF1	Coffee	£11.23

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

The COO, though, likes low prices and wants people buying strawberries to get a price discount for bulk purchases. If you buy 3 or more strawberries, the price should drop to £4.50.

Our check-out can scan items in any order, and because the CEO and COO change their minds often, it needs to be flexible regarding our pricing rules.

The interface to our checkout looks like this (shown in ruby):

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

Implement a checkout system that fulfills these requirements.

Test data

Basket: GR1,SR1,GR1,GR1,CF1
Total price expected: £22.45

Basket: GR1,GR1
Total price expected: £3.11

Basket: SR1,SR1,GR1,SR1
Total price expected: £16.61

Implementation

Two classes have been defined: Checkout and PricingRule.

PricingRule Class

Checkout Class