DataLoader fails promise when Error is returned

dataloader.spec.js

import { expect } from 'chai'
import DataLoader from 'dataloader'
import sinon from 'sinon'

function createByIdLoader(loadFunc) {
  return new DataLoader(
    ids => Promise.all(
      ids.map(loadFunc)
         .map(promise => promise.catch(err => new Error(err)))
    ),
    {
      cache: false
    }
  )
}

describe('DataLoader', () => {
  it('should return values when promises are fulfilled', () => { // Working
    const value = 'success'
    const stub = sinon.stub().returns(Promise.resolve(value))
    const loader = createByIdLoader(stub)

    return loader.loadMany([1, 2]).then(values => {
      expect(values).to.deep.equal([value, value])
    })
  })

  it('should return errors when promises are rejected', () => {  // Failing
    const value = 'fail'
    const stub = sinon.stub().returns(Promise.reject(value))
    const loader = createByIdLoader(stub)

    return loader.loadMany([1, 2]).then(errors => {
      expect(errors).to.deep.equal([new Error(value), new Error(value)])
    })
    .catch((err) => {
      console.log('Should never be here')
      throw err
    })
  })
})