I stripped down the project but the same problem occurs.
So running the tests for the core project only does not work with buildship.
Running the tests over the root project works.
Running in the command line ‘./gradlew clean core:test’ also works
Your ‘core’ project contains a settings.gradle, which it should not. There should only be one settings.gradle in the root project, where you reference all sub projects of your build. See the documentation on multi-project builds.