javascript – Mocha API Testing: getting 'TypeError: app.address is not a function'-ThrowExceptions

Exception or error:

My Issue

I’ve coded a very simple CRUD API and I’ve started recently coding also some tests using chai and chai-http but I’m having an issue when running my tests with $ mocha.

When I run the tests I get the following error on the shell:

TypeError: app.address is not a function

My Code

Here is a sample of one of my tests (/tests/server-test.js):

var chai = require('chai');
var mongoose = require('mongoose');
var chaiHttp = require('chai-http');
var server = require('../server/app'); // my express app
var should = chai.should();
var testUtils = require('./test-utils');


describe('API Tests', function() {
  before(function() {
    mongoose.createConnection('mongodb://localhost/bot-test', myOptionsObj);

  beforeEach(function(done) {
    // I do stuff like populating db

  afterEach(function(done) {
    // I do stuff like deleting populated db

  after(function() {

  describe('Boxes', function() {

    it.only('should list ALL boxes on /boxes GET', function(done) {
        .end(function(err, res){

    // the rest of the tests would continue here...



And my express app files (/server/app.js):

var mongoose = require('mongoose');
var express = require('express');
var api = require('./routes/api.js');
var app = express();

mongoose.connect('mongodb://localhost/db-dev', myOptionsObj);

// application configuration

// routing set up
app.use('/api', api);

var server = app.listen(3000, function () {
  var host = server.address().address;
  var port = server.address().port;

  console.log('App listening at http://%s:%s', host, port);

and (/server/routes/api.js):

var express = require('express');
var boxController = require('../modules/box/controller');
var thingController = require('../modules/thing/controller');
var router = express.Router();

// API routing
router.get('/boxes', boxController.getAll);
// etc.

module.exports = router;

Extra notes

I’ve tried logging out the server variable in the /tests/server-test.js file before running the tests:

var server = require('../server/app'); // my express app

console.log('server: ', server);

and I the result of that is an empty object: server: {}.

How to solve:

You don’t export anything in your app module. Try adding this to your app.js file:

module.exports = server


It’s important to export the http.Server object returned by app.listen(3000) instead of just the function app, otherwise you will get TypeError: app.address is not a function.



const koa = require('koa');
const app = new koa();
module.exports = app.listen(3000);


const request = require('supertest');
const app = require('./index.js');

describe('User Registration', () => {
  const agent = request.agent(app);

  it('should ...', () => {


This may also help, and satisfies @dman point of changing application code to fit a test.

make your request to the localhost and port as needed


instead of


this fixed the same error message I had using Koa JS (v2) and ava js.


The answers above correctly address the issue: supertest wants an http.Server to work on. However, calling app.listen() to get a server will also start a listening server, this is bad practice and unnecessary.

You can get around by this by using http.createServer():

import * as http from 'http';
import * as supertest from 'supertest';
import * as test from 'tape';
import * as Koa from 'koa';

const app = new Koa();

# add some routes here

const apptest = supertest(http.createServer(app.callback()));

test('GET /healthcheck', (t) => {
    .expect(res => {
      t.equal(res.text, 'Ok');


We had the same issue when we run mocha using ts-node in our node + typescript serverless project.

Our tsconfig.json had “sourceMap”: true . So generated, .js and files cause some funny transpiling issues (similar to this). When we run mocha runner using ts-node. So, I will set to sourceMap flag to false and deleted all .js and file in our src directory. Then the issue is gone.

If you have already generated files in your src folder, commands below would be really helpful.

find src -name “” -exec rm {} \;
find src -name “
.js” -exec rm {} \;

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