Twilio Functions utils library

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Twilio Functions Utils


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This lib was created with the aim of simplifying the use of serverless Twilio, reducing the need to apply frequent try-catches and improving context management, making it no longer necessary to return the callback() method in all functions.


npm install twilio-functions-utils


The lib provides a function useInjection who returns a brand function for every execution. This returned function is ready to receive the Twilio Handler arguments and make them available as this properties as this.request, this.cookies and this.env at the Function level and this.client and this.env at the Provider function level.

useInjection(Function, Options) Function

The useInjection method takes two parameters. The first to apply as a handler and the last is an object of configuration options.
useInjection Function Function
Must be writen in standard format, this will be your handler function.
function createSomeThing (event) {
useInjection Options.providers Object
An object that can contain providers that will be defined, which act as use cases to perform internal actions in the handler function through the this.providers method.
useInjection Options.validateToken Boolean
You can pass validateToken equal true to force Flex Token validation using Twilio Flex Token Validator
    providers: { create, remove },
    validateToken: true

When using Token Validator, the Request body must contain a valid Token from Twilio Flex.
// Event
  Token: "Twilio-Token-Here"

Response Class

The responses coming from the function destined to the handler must be returned as an instance of Response.
Response receives a string and a number (status code):
return new Response('Your pretty answer.', 200);

There are two failure response models, BadRequest and NotFound. Its use follows the same model.
const notFound = new NotFoundError('Your error message here.');
const badRequest = new BadRequestError('Your error message here.');

TwiMLResponse Class

There is a proper response template to use with the TwiML format:
const twimlVoice = new Twilio.twiml

const enqueueVoice = twimlVoice

return new TwiMLResponse(twimlVoice, 201)


IMPORTANT TO USE REGULAR FUNCTIONS ➜ With arrow functions it doesn't work as expected as this cannot be injected correctly.
function yourFunctionName() {
  // ...

Separate your actions from the main routine of the code. Break it down into several smaller parts that interact with your event, to facilitate future changes. You can create functions such as Assets or Functions, then just import them through the Runtime and pass them to the provider.
// File: assets/create.private.js

const { Result } = require('twilio-functions-utils');

 * Here you can acess  Twilio Client as client and Context as env (so you can get env vars).
 * @function
 * @param { object } event
exports.create = async function (event) {
  const { client, env } = this

  return Result.ok(await new Promise((resolve, reject) => {
    const random = Math.random();

    if (random >= 0.5) {
      return resolve({ sucess: 'Resolved' });
    return reject(new Error('Unresolved'));

In your handler you will have access to the function through the providers property, internal to the this of the function that precedes the handler.
// File: functions/create.js

const { useInjection, Response } = require('twilio-functions-utils');
const { create } = require(Runtime.getAssets()['/create.js'].path)

 * @typedef { object } CreateActionThis
 * @property { object } request
 * @property { object } cookies
 * @property { object } env
 * @property { string } env.DOMAIN_NAME
 * @property { object } providers
 * @property { create } providers.create

 * You can perform all your "controller" level actions, as you have access to the request headers and cookies.
 * Then just call the providers you provided to handler by using useInjection.
 * Just put it on a Response object and you are good to go!
 * @function
 * @param { object } event
 * @this CreateActionThis
async function createAction(event) {
  const { cookies, request, env } = this
  const providerResult = await this.providers.create(event)

  if (providerResult.isError) {
    return new BadRequestError(providerResult.error);

  return new Response(, 201);

exports.handler = useInjection(createAction, {
  providers: {
  validateToken: true, // When using Token Validator, the Request body must contain a valid Token from Twilio.


typeOf(Value) Function

A simple method to discovery a value type. This is more specific then the original JavaScript typeof.
It will return as Array, Object, String, Number, Symbol.
typeOf Value
Could be any JavaScript primitive value to be type checked.


const { typeOf } = require('twilio-functions-utils');

const type = typeOf('my name is Lorem');
const typeArray = typeOf(['one', 'two']);
const original = typeof ['one', 'two']

console.log(type) // String
console.log(typeArray) // Array
console.log(original) // object

Result Class

The Result class provides an organized and simple way to return errors without having to wrap every request in Try Catches.


Use the .ok method to create a new Result instance with a data property and isError false.
Result.ok data
The data value could be of any of the primitives types that javascript accpets.
Use the .failed method to create a new Result instance with an error property and isError true.
Result.failed error (Error|)
The data value must be preferably of Error type, but you can use any of the primitive ones...


A boolean propety that return true when Result contain a defined error value.
The successfully returned value.
An Error like object throwed by the "action" as result.


const result = Result.ok(value);
// or
const result = Result.ok(await value);
// or
const result = Result.failed(error);

if (result.isError) {
  return new BadRequestError(result.error)

return new Response(


useMock(Function, Options) Function

The Twilio Serverless structure make it hard for testing sometimes. So this provides a method that works perfectly with useInjection ready functions. The useMock act like useInjection but mocking some required fragments as getAssets and getFunctions.
useMock Function Function
The same function as used in useInjection.
useMock Options.providers Object
Unlike useInjection, the useMock method only receives the Options.providers property.


(Required) Set your jest testing script with NODE_ENV=test:
"scripts": {
    "test": "NODE_ENV=test jest --collect-coverage --watchAll",
    "start": "twilio-run",
    "deploy": "twilio-run deploy"

Your files structures must be have assets and functions into first or second levels starting from src (when in second level):
├─ package.json
├─ node_modules/
├─ src/
│  ├─ functions/
│  ├─ assets/

├─ package.json
├─ functions/
├─ assets/
├─ node_modules/

Exports your function to be tested and your handler so it can be used by Twilio when in runtime:
async function functionToBeTested(event) {
  const something = await this.providers.myCustomProvider(event)
  return Response(something)

const handler = useInjection(functionToBeTested, {
  providers: {

module.exports = { functionToBeTested, handler }; // <--

(Required) You always need to import the twilio.mock for Response Twilio Global object on your testing files begining.

Use Twilio Functions Utils useMock to do the hard job and just write your tests with the generated function. You can use Twilio.mockRequestResolvedValue, Twilio.mockRequestImplementation, Twilio.mockRequestRejectedValue to Mock your Twilio API requests.
/* global describe, it, expect */


const { useMock, Response } = require('twilio-functions-utils');
const { functionToBeTested } = require('../../functions/functionToBeTested'); // <-- Import here!

// Create the test function from the function to be tested
const fn = useMock(functionToBeTested, {
  providers: {
    myCustomProvider: async (sid) => ({ sid }), // Mock the providers implementation.
  env: {
    YOUR_ENV_VAR: 'value'
  client: {
    functionToMock: {}

describe('Function functionToBeTested', () => {
  it('if {"someValue": true}', async () => {
    const request = { TaskSid: '1234567', TaskAttributes: '{"someValue": true}' };

      statusCode: 200,
      body: {
        sid: '1234567'
      statusCode: 200,
      body: {
        key: "MP****",
        data: { sid: '7654321' }

    const res = await fn(request);
    const customMap = await Runtime.getSync().maps("MP****").fetch();

    expect({ sid: '7654321' });
    expect(res.body).toEqual({ sid: '1234567' });