In my case, the culprit was not distinguish the main and test sources folder within pom.xml (generated by eclipse maven project)
<build>
<sourceDirectory>src</sourceDirectory>
....
</build>
If you override default source folder settings in pom file, you must explicitly set the main AND test source folders!!!!
<build>
<sourceDirectory>src/main/java</sourceDirectory>
<testSourceDirectory>src/test/java</testSourceDirectory>
....
</build>