Internal wallet transactional system test task

Goal: Internal wallet transactional system (with a front end)

Requirements:

• Based on relationships every entity e.g. User, Team, Stock or any other should have their own defined “wallet” to which we could transfer money or withdraw
• Every request for credit/debit (deposit or withdraw) should be based on records in database for given model
• Every instance of a single transaction should have proper validations against required fields and their source and target wallet, e.g. from who we are taking money and transferring to whom? (Credits == source wallet == nil, Debits == target wallet == nil)
• Each record should be created in database transactions to comply with ACID standards
• Balance for given entity (User, Team, Stock) should be calculated by summing records

Tasks:

1. Architect generic wallet solution (money manipulation) between entities (User, Stock, Team or any other)
2. Create model relationships and validations for achieving proper calculations of every wallet, transactions
3. Use STI (or any other design pattern) for proper money manipulation

Application must consists of:

• Back-end (preferably Rails) + tests of business logic: validations, operations, edge-cases (preferably RSpec)
• Front-end (any framework)

Application architecture: Entity–relationship model

┌─────────────────────────────────────────────────┐
│ User (Devise)                                   │
│─────────────────────────────────────────────────│
│ PK id integer NOT NULL                          │
│ email char(100) NOT NULL, UNIQUE CONSTRAINT     │
│ role = person | team | stock - integer NOT NULL │
└─────────────────┬───────────────────────────────┘
                  │
                  │ 1:1
                  ▼
┌───────────────────────────────────────────────────┐
│ Wallet                                            │
│───────────────────────────────────────────────────│
│ PK id integer NOT NULL                            │
│ FK user_id integer NOT NULL                       │
│ balance float (cumulative after each transaction) │
└─────────────────┬─────────────────────────────────┘
                  │
                  │ 1 mandatory:many optional
                  ▼
┌───────────────────────────────────────────────────┐
│ Transaction                                       │
│───────────────────────────────────────────────────│
│ PK id integer NOT NULL                            │
│ FK1 source_wallet_id integer NOT NULL             │
│ FK2 target_wallet_id integer NOT NULL             │
│ amount float NOT NULL                             │
│ created_at datetimez NOT NULL                     │
└───────────────────────────────────────────────────┘

Technologies

• Puma as simple, fast, multi-threaded server for Ruby/Rack applications
• Rake – Ruby Make, make-like build utility for Ruby
• All required gems installed with Bundler gem manager
• Devise - Flexible authentication solution for Rails with Warden.
• Letter Opener - Preview mail in the browser instead of sending.
• Testing:
  • RSpec - testing tool for TDD/BDD
  • rspec-rails - RSpec testing framework for Ruby on Rails
  • Fuubar - instafailing RSpec formatter that uses a progress bar instead of a string of letters and dots as feedback.
  • factory_bot, factory_bot_rails - fixtures replacement with a straightforward definition syntax, support for multiple build strategies (saved instances, unsaved instances, attribute hashes, and stubbed objects), and support for multiple factories for the same class (user, admin_user, and so on), including factory inheritance + provides Rails integration.
  • Faker - A library for generating fake data such as names, addresses, and phone numbers.
  • Shoulda Matchers - Simple one-liner tests for common Rails functionality.
• Debug: Awesome Print - Pretty print your Ruby objects with style -- in full color and with proper indentation
• Code style is provided via RuboCop
• TODO: add more

Requirements

• System: Linux, Mac
• Git
• SQLite3
• Node.js
• Yarn
• Ruby version manager (rbenv or RVM)
• Ruby 3.0.2
• Bundler
• Gems installed via Bundler Gemfile

Installation

Download code from repository

Clone with SSH (or HTTPS):

$ git clone [email protected]:alex-petr/internal-wallet-transactional-system.git internal_wallet_transactional_system

Update the packages (formulae) and Homebrew itself

$ cd internal_wallet_transactional_system/ && brew update && brew upgrade ; brew cleanup

rbenv (for macOS)

$ brew install rbenv

Ruby

$ rbenv install 3.0.2

Install Bundler and all required gems

$ gem install bundler && bundle

Install front-end packages

$ yarn install

Run all pending migrations

$ rails db:migrate && rails db:migrate RAILS_ENV=test

Create seed data from db/seeds.rb

$ rails db:seed

TODO: add NVM/NPM/NodeJS

TODO: add database setup (create/add seeds data)

Configuration

TODO: add info about .env files

Run application

Start Rack & Puma web application

# On default 3000 port:
$ rails s

# With customized port (-p, --port PORT):
$ rails s -p 5000

Navigate to any of these URLs:

• http://lvh.me:3000
• http://localhost:3000
• http://127.0.0.1:3000

Run tests

# Default: Run all spec files (i.e., those matching spec/**/*_spec.rb)
$ rspec

# Run all spec files in a single directory (recursively)
$ rspec spec/services

# Run a single spec file
$ rspec spec/services/some_service_spec.rb

TODOs for further improvement

• Migrate to MySQL or PostgreSQL
• Add Brakeman, RubyCritic
• Add annotate, dotenv-rails, pry-byebug
• Improve Readme
• Move transaction operations to Sidekiq background workers
• Add CI (Drone.io, Circle CI etc): RuboCop, RSpec, Brakeman
• Add errors monitoring system (Rollbar, Sentry, Airbrake etc)
• Add Cucumber/Capybara feature tests
• Migrate to Rails JSON API and remove views to separated repo
• Migrate from custom Rails API to Grape API / Swagger
• Add RailsMoney gem