Analysis of unit test coverage

### What

Unit testing current provides line coverage and function coverage significantly below 100%.
This task will analyze each uncovered code section and recommend countermeasures.

### Acceptance Criteria (DoD)

Plan for adapting the test configuration or adding unit testing for code sections currently not covered by unit tests.

### How

Initial analysis shows that code section not covered by unit tests include stubs and mocks. These code sections can be excluded from coverage measurement, using "coverage --instrumentation_filter" in .bazelrc.
All code sections not covered by unit tests will be evaluate if they are productive code that should be covered by unit tests and if/how they can be covered by unit tests.