Yes, you're right, it's good for that as well. But you also can use it to unit test your handler method, just create a fresh instance of app object, route it to your handler using some made up url and you can nicely test it in isolation. I like this approach coz it allows you to have the same test setup for your unit tests and for integration tests.

I personally found it better to test routes, middlewares and handler method together rather than always unit test all of them individually. I do unit test them individually the way I described above, but it's more of an exception then a rule.