Boilerplate for promise fallback kata (for Medium article)

first-result.js

const firstResult = (services) => { /* … */ }

firstResult([
  () => Promise.resolve([]),
  () => Promise.resolve(['Berlin']),
  () => console.error('Do not call me!')
])
  .then((result) =>
    console.assert(result[0] === 'Berlin', 'Test1 failed!')
  )

firstResult([
  () => Promise.resolve([]),
  () => Promise.resolve([])
])
  .then((result) =>
    console.assert(result.length === 0, 'Test2 failed!')
  )

firstResult([])
  .then((result) =>
    console.assert(result.length === 0, 'Test3 failed!')
  )

firstResult([
  () => Promise.reject('timeout'),
  () => Promise.resolve(['Berlin'])
])
  .then(() => console.error('Should be rejected!'))
  .catch((reason) =>
    console.assert(reason === 'timeout', 'Test4 failed!')
  )