I've done a little bit of this.
I have a backend application that's stand alone - that does ocr- for documents submitted. So- it figures out what machine to delegate to.
The front end however is just a simple front end. It doesn't deal with any of the details. It just takes input- checks it for common sense-ness- and passes it along. CGI::Application.

I used hacks to t/est. I regex into the return of CGI::Application- the returned html code of a 'pageview'.

Ultimately I have to check it via hand to really know. It's not easy to test.t html output.