Cresh Backend Engineering Technical Tests - Javascript Flavor

This is a little challenge to help us assess your skills as a developer.

A particular attention will be taken to your Code Structure, your ability to implement the data model and organize the whole project.

Context

At Cresh we provide credit at shopping cart, instantly. We aim to ease the way consumers can get the products they want from any shop, both online and instore.

To do so, we provide several apps, both B2B and B2C along with some APIs.

Instructions

We would like you to reproduce some (very simplified) functionalities related to our business model.

To realize this test you can use any of the node web application framework you are the most confortable with.

You will also need to choose a database to put and get your data from. We would prefer you to use a RDBMS for this test, but if you are more confortable with a NoSQL one like MongoDB, that's fine too.

We want you to implement a small API able to create and get some transactions customers have made shopping at some stores and interact with them.

A few key points :

• A customer can have several transactions ;
• A transaction must have as many instalments as its split attribute ;
• When a transaction is created, all its instalments are also generated based on the current date and the split attribute. Only the first payment is paid immediately, the transaction as a whole is not done yet ;
• When calculating each instalment amount, if you can't have an exact split, the remainder is to be added to the first one ;
• When all instalments of a transaction have been paid off, its is_completed flag must be switched to true.

Data model

Note: Relations between tables and default values are voluntarily left out for you to guess.

customers

Name	Type	Description
id	integer	Primary Key
name	varchar(255)	Name of the customer
created_date	date	Date of creation

transactions

Name	Type	Description
id	integer	Primary Key
store_name	varchar(50)	Name of the store where the transaction was made
amount	integer	Transaction's full amount, in cents
split	integer	Number of instalments for the transaction
is_completed	boolean	Have all instalments been paid off ?
created_date	date	Date of creation

instalments

Name	Type	Description
id	integer	Primary Key
amount	integer	Instalment amount, in cents
is_paid	boolean	Is the payment done yet
planned_date	date	Planned date of payment
paid_date	date	Actual payment date

API Documentation

Route	Method	Query String	Body	Description
/ping	GET	-	-	See if the service is running properly, including the DB
/customers	GET	-	-	List of customers
/customers	POST	-	name	Create a customer
/customers/:id/transactions	GET	-	-	List of transactions for a specific customer
/transactions	POST	-	store_name amount split user_id	Create a transaction
/transactions/:id/instalments	GET	-	-	List of a transaction's instalments
/transactions/:id/instalments	PUT	-	-	Trigger the payment of the transaction's next instalment

What's evaluated

• Cleanliness & structure of the code
• Code extensibility
• Documentation
• Respect of KISS and DRY principles
• Use of git commits

Bonus points

• Writing unittests
• Using Typescript
• Using containers for both the api and the database

Deliverable

Please clone this repository and send us a zip or a link to your repo.

We expect :

• A clean files structure
• Some commands to run from the package.json
• A documentation on how to install, start and use this API

Good luck and have fun !

Getting started

Make sure to have docker installed, otherwise docs.docker.com/get-docker will help you.

1. Clone the project
2. Install dependencies

  cd cresh-api && yarn install

3. Config environment variables

  cp .env.example .env
  cp docker.env.model docker.env

edit docker.env and .env to match your environment 4. Start db container

  yarn docker:up

5. Initialize the database

   yarn init:db (create database and tables)

6. Start the server

  yarn start

7. Api is available at http://localhost:3000

Other command

#Stop db container
  yarn docker:down
#watch mode
  yarn start:dev
#production mode
  yarn start:prod
#eslint
  yarn lint
#prettier
  yarn format

Test

#launch test
  yarn test
#watch mode
  yarn test:watch
#test coverage
  yarn test:cov