Improve code coverage

**Is your feature request related to a problem? Please describe.**

Code coverage is low because of insufficient tests

**Describe the solution you'd like**

Add tests to bring the coverage up.

**Additional context**

Tests are written in spock groovy framework.

Start by locating the existing Spock/Groovy test suite and the Java/Xtext runtime areas it exercises. Review the current coverage results to identify untested behavior, then add focused tests. Done means the coverage has increased and the new tests pass.

Written by the indexing model from the issue text.