mvn compile fails if test-jar of parallel-consumer-core was not previously installed / deployed.

Due to a bug in maven handling of test-jar dependencies - running `mvn compile` fails, unless `mvn install` or `mvn deploy` was executed previously to create test-jar of parallel-consumer-core.
See [stackoverflow - why is "test-jar" dependency required for "mvn compile"](https://stackoverflow.com/questions/4786881/why-is-test-jar-dependency-required-for-mvn-compile).

Start by inspecting the repository's Maven build configuration and the test-jar dependency described in the issue. Run `mvn compile` from a clean checkout without first running `mvn install` or `mvn deploy`; the work is done when compilation succeeds in that state.

Written by the indexing model from the issue text.