Tests: Increase test coverage

[Zen-CODE]

This PR is (hopefully) the first of many to extend test coverage. Even through the tests my not be thorough, at least it adds coverage and gives as starting point for more meaningful coverage.

My current strategy is to generate coverage report stats and to systematically start targeting test at lines of uncovered code. Rather than accumulate a massive PR, bit my bit makes it easier to review and manage.

Maintainer merge checklist

• Title is descriptive/clear for inclusion in release notes.
• Applied a Component: xxx label.
• Applied the api-deprecation or api-break label.
• Applied the release-highlight label to be highlighted in release notes.
• Added to the milestone version it was merged into.
• Unittests are included in PR.
• Properly documented, including versionadded, versionchanged as needed.