Create automated tests

Problem/Motivation

Without automated tests, we can't refactor without assurance we don't break functionality

Proposed resolution

Create tests to assure us that:
- The mega-menu content entity can be created
- The REST link exists and produces sensible results
- The javascript is capable of attaching a mega-menu content entity to an associated menu item

Remaining tasks

Patch
Test
Add tests to the project so they run automatically

User interface changes

none

API changes

none

Data model changes