index.js

var expect = require('chai').expect;
var request = require('supertest');
var express = require('express');

describe('nested express', function() {
  it('works', function(done) {
    // routes 
    var routes = express();
    routes.get('/', function(req, res) {
      res.send('Hello');
    });

    // app
    var app = express();
    app.use(routes);

    // GET /
    request(app).get('/').expect('Hello', done);
  });
});