order-total.js

function orderTotal(fetch, order) {
  fetch('https://vatapi.com/v1/country-code-check?code=' + order.country)
  return Promise.resolve(order.items.reduce((prev, cur) =>
    cur.price * (cur.quantity || 1) + prev, 0))
}

module.exports = orderTotal

order-total.test.js

const orderTotal = require('./order-total')

const emptyFunction = () => {}

it('calls vatapi.com correctly', () => {
  let isFakeFetchCalled = false
  const fakeFetch = (url) => {
    expect(url).toBe('https://vatapi.com/v1/country-code-check?code=DE')
    isFakeFetchCalled = true
  }
  orderTotal(fakeFetch, {
    country: 'DE',
    items: [
      { 'name': 'Dragon waffles', price: 20, quantity: 2 }
    ]
  }).then(result => {
    expect(isFakeFetchCalled).toBe(true)
  })
})

it('if country code specified')

it('Quantity', () =>
  orderTotal(emptyFunction, {
    items: [
      { 'name': 'Dragon candy', price: 2, quantity: 3 }
    ]
  }).then(result => expect(result).toBe(6)))

it('No quantity specified', () =>
  orderTotal(emptyFunction, {
    items: [
      { 'name': 'Dragon candy', price: 3 }
    ]
  }).then(result => expect(result).toBe(3)))

it('Happy path (Example 1)', () =>
  orderTotal(emptyFunction,{
    items: [
      { name: 'Dragon food', price: 8, quantity: 1 },
      { name: 'Dragon cage (small)',  price: 800, quantity: 1 }
    ]
  }).then(result => expect(result).toBe(808)))

it('Happy path (Example 2)', () =>
  orderTotal(emptyFunction, {
    items: [
      { name: 'Dragon collar', price: 20, quantity: 1 },
      { name: 'Dragon chew toy',  price: 40, quantity: 1 }
    ]
  }).then(result => expect(result).toBe(60)))

package.json

{
  "name": "test-runners",
  "version": "1.0.0",
  "description": "",
  "main": "code-and-tests.js",
  "scripts": {
  "test": "jest",
    "watch": "jest --watch *.js"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "jest": "^21.2.1"
  }
}

sandbox.js

const fetch = require('node-fetch')

const result =
  fetch('https://vatapi.com/v1/country-code-check?code=DE', {
    headers: {
      'apikey': process.env.VAT_API_KEY
    }
  })
  .then(response => response.json())
  .then(data => data.rates.standard.value)

result