Backend Ruby Challenge

✨ Introduction

Welcome to the coding challenge for developers interested in backend roles in Kelisto. It's not an against-the-clock time challenge - you can complete it at home in your own time.

Ideally you will return your submission in within 1 week - the sooner you get your submission back to us, the more quickly we can progress your application to interview stage. Based on previous candidate experiences, we believe it will take you between 2 to 4 hours to complete the challenge.

The Challenge

Build a Checkout Cart. It consists in:

• Modeling business rules.

Modeling business rules

• Implement a check-out system that fulfills business requirements.

We expect only plain classes and objects to solve the challenge. Add files for your solution to the src folder.

Business requirements

• Build a check-out system.
• Our check-out let us to scan items.
• Our check-out can calculate the total price of those scanned items.
• We sell only three kind of items:

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

• Our check-out support receiving different pricing rules to handle different discounts depending on the scanned items. These are the pricing rules:
  • buy-one-get-one-free offers and of green tea.
  • 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 product team change their minds often, it needs to be flexible regarding our pricing rules.

Usage

• The interface to our check-out looks like this:

const co = new Checkout(pricing_rules)

co.scan(item)
co.scan(item)

const price = co.total

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

🎁 Bonus Round (not required but nice-to-have)

• Add unit tests
• Dockerize the app
• Surprise us…

👎 What we do not like

• Frameworks 😊 (you don't need to use Rails or any other; just use PLAIN ruby).

💯 How we're evaluating the result

Prioritised from most important to least important, here's our evaluation criteria:

• Code Quality. Is the code clean, well-structured and easy to understand?
• Architecting. Did you isolate responsabilities? Did you use any software pattern?
• Testing. Did you write tests?
• The extra mile. Did you document your solution? (use the ABOUT.md file)

You do not need to hit all points, but obviously, the more the better :)

🚀 Project submitting

To send us your code, you can:

• Make a fork of this repository, and send us a pull-request;
• or give access to your repository in Github/Bitbucket.

🤘 What’s next?

Once you submit your solution, our team will review your code challenge, taking your experience level into account. The sample code provided by you should be in a state considered as a "production" ready - where each requested element is prepared and potentially ready to review with your colleagues.

Good luck!

“The Challenge” has been created with the sole intention of being used as a guiding document for the current recruitment process. This means we won't be using it (all or parts of it) within our projects.