This additional constraint enables adding a route to the template (and p...

...otentially to the UseMvc method) without actually implementing the actual artifact.

For example without adding an area to a controller, a route can still be added to the template.
This should be inside the site, don't leave this kind of code in the tests. It's not ok to change the site this way. I'm ok with pushing as it but file a bug and immediately submitting a PR to fix it. 

The idea here is to come up with the right pattern for functional testing, and not just get a feature in.