tests/improving-coverage

this pull request is comprised of code coverage additions.
it's, roughly, a five percent increase.

three changes were made in this branch that were not test class changes:

- altered the structure of two methods of `rosafactory` to ease testability
- removed an unused constructor for `rosaexception`
- removed a redundant `rosafactory#setUp` invocation in `responsesresource` (`rosafactory#rebuild` already calls `setUp`)