Description

Thanks for your interest in notonthehighstreet.com. We would like to progress your application, so the second stage of our process is to ask you to complete a short object oriented programming test. Please follow the instructions below, complete in Ruby, and return your answer to us by email as soon as you can.

notonthehighstreet.com is an online marketplace, here is a sample of some of the products available on our site:

Product code	Name	Price
001	Travel Card Holder	£9.25
002	Personalised cufflinks	£45.00
003	Kids T-shirt	£19.95

Our marketing team want to offer promotions as an incentive for our customers to purchase these items.

If you spend over £60, then you get 10% off your purchase
If you buy 2 or more travel card holders then the price drops to £8.50.

Our check-out can scan items in any order, and because our promotions will change, it needs to be flexible regarding our promotional rules.

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

co = Checkout.new(promotional_rules)

co.scan(item)

co.scan(item)

price = co.total

Implement a checkout system that fulfills these requirements.

Test data

Basket: 001,002,003

Total price expected: £66.78

Basket: 001,003,001

Total price expected: £36.95

Basket: 001,002,001,003

Total price expected: £73.76

Solution

Checkout takes array of rules and applies them in given order to all items whenever total needs to be calculated. Each rule's apply methods accepts:

items - list of all items scanned so far
basket_total - prices of all items in basket with previous rules applied

Dependencies

Code was implemented using MRI Ruby 2.2.2. Code uses keyword arguments, so it will not work with versions older then 2.0. There is no dependencies of external libraries.

Testing

To avoid installing dependencies tests are implemented with Ruby's Minitest library.

To run tests run following command from application's directory:

$ bin/test

To run individual test (in this case feature test):

ruby -Iapp:specs specs/features/checkout_with_promotions_spec.rb

Test hierarchy

There are two kinds of tests:

ones in specs/app are testing individual classes (unit tests)
one in specs/features has tests that covers requirements from description (feature/functional tests)

Trying out

To try out different scenarios I've included runner that let scan items (type product codes) and see baskets total and total with discount.

$ bin/run

and then just follow instructions

##Author

Arturs Meisters 21/06/2016

kalifs / notonthehightstreet