Пытаюсь резолвить промисы пачками по N штук, а не все сразу, как делает Promise.all

index.js

'use strict';

const flatten = (arr) => [].concat.apply([], arr)
/**
 * Accepts an iterate collection of promises, resolves them by bundles with accumulate results
 *
 * @param   {Array}  promises           - array of unresolved promises
 * @param   {object} settings           - object with any settings
 * @param   {number} settings.from      - number of promise, from which to begin new iteration
 * @param   {number} settings.iteration - number of promises for one iteration
 * @returns {Array}                     - returns promise
 */
const debouncePromises = async (promises, settings) => {
    const defaults = {
        from: 0,
        iteration: 10
    }
    const options = Object.assign({}, defaults, settings)

    let pack = []
    let results = []

    for (let index = 0; index < promises.length; index += options.iteration) {
        pack = promises.slice(index, index + options.iteration)
        results.push(await Promise.all(pack))
    }

    return flatten(results)
}

module.exports = debouncePromises

index.test.js

import test from 'ava'
import debouncePromises from './index.js'

test('жить охуенно', t => {
    const promises = new Array(30).fill(() => {
        return new Promise(resolve => {
            resolve('result')
        })
    })

    return debouncePromises(promises)
        .then(result => {
            t.true(
                result.every(el =>
                    el() === 'result'
                )
            )
        })
})