My apologies I wasn't too specific. I was meaning a controller through express. It's not as straightforward as you would expect with code buried throughout on how to set it up. This is a typical barrier for developers to not test as much.
If you set up your controllers so that they are independent from the routes, then they are just as easy to test.
It could be as simple as: app.get('/users/:id', userController.userPage). You can then test userController.userPage(req, res, next) instead of the route.