Hot to test modular routes in Express

In one file I have ..

const express = require('express');
const app = express();
app.use(// various middleware);
app.use(routes)

module.exports = app;

In my routes.js file I have some basic routes set up which I mount on app (above file).

My question is I want to test the routes, but with all the various middleware attached. I'm using Mocha / Chai for testing.

I'm importing app from the first file.

const res = await chai
      .request(app)
      .get('/')
      .set('cookie', `some_cookie=${cookie_value}`);

Is this the correct way? It doesn't seem to work. If I import the routes file, I'm assuming that is testing just the routes with no middlware.