Add tests to guides, controllers, and respective APIs

### What's still missing.

* Various Update tests, largely because a) those are handled through the API and b) I'm not sure how to test these.
* 404 object not found tests on both api and non-api controllers.
* User Registration and application controller tests, because I don't know much about those at all.
Incorrect indentation detected (column 4 instead of 2).