Restore test coverage with gradle

[ursjoss]

Before moving to gradle (with maven) and the related restructuring of the project, the test coverage in sonarcloud was at more than 97%. The current state of PR #83 only achieves 76.4% test coverage. I suspect that my current setup does not merge the coverage from unit tests with that of integration tests.

I decided to pull this out of #83 into a separate issue, so I can merge #83 and get on with functional changes.

The goal of this issue is to restore the full coverage as it was before.