## users/users-repository.js ####################
const users = new Map()
exports.create = user => users.set(user.username, user)
exports.read = username => users.get(username)

## users/users.js ###############################
const defaultUsersRepo = require('./users-repository')
module.exports = (usersRepo = defaultUsersRepo) => {
  return {
    create: user =>  {
      if (!user.username || !user.email || !user.hashPassword || user.hashPassword.length < 8)
        return false

      usersRepo.create(user)
      return true
    },
    read: username => usersRepo.read(username)
  }
}

## users/users.spec.js ##########################
const mockUsersRepo = () => {
  const users = new Map()
  return {
    create: (user) => users.set(user.username, user),
    read: (username) => users.get(username)
  }
}
const assert = require('assert')
const users = require('./users')(mockUsersRepo())
assert(users.create({username: 'bob', email: 'example@example.com', hashPassword: 'A$%Hsdf&/F'}))
const user = users.read('bob')
assert(user)
assert.equal(user.username, 'bob')
assert.equal(user.email, 'example@example.com')
assert.equal(user.hashPassword, 'A$%Hsdf&/F')
assert(!users.create({username: 'bob', hashPassword: 'A$%Hsdf&/F'}))
assert(!users.create({username: 'bob', email: 'example@example.com', hashPassword: 'HHR$'}))

## users/index.js ###############################
const users = require('./users')
const usersRepo = require('./users-repository')
exports.users = users
exports.usersRepo = usersRepo

## app.js #######################################
// const users = require('./users').users((require('./users').usersRepo)) // without default parameters
const users = require('./users').users() // using default parameters

if (!users.create({username: process.env.USERNAME, email: process.env.EMAIL, hashPassword: process.env.HASH_PASSWORD}))
  throw new Error('Invalid user\'s information')
console.log(users.read(process.env.USERNAME))