I know the other tests in this project probably haven't been updated to use this yet, but we have a new macro that makes this kind of testing better/safer:

https://github.com/puppetlabs/trapperkeeper/blob/master/doc/test-utils.md#with-app-with-cli-data

I don't mind merging this w/o that change, but if you were inclined to port your tests over to use that I think it would be good.  We should try to lean towards using the new macros for all new tests.