Maven: Source Encoding in UTF-8 not working?

I have found a “solution” myself:

I had to pass the encoding into the maven-surefire-plugin, but the usual

<encoding>${project.build.sourceEncoding}</encoding>

did not work. I still have no idea why, but when i pass the command line arguments into the plugin, the tests works as they should:

<plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-surefire-plugin</artifactId>
      <version>2.15</version>
      <configuration>
        <argLine>-Dfile.encoding=UTF-8</argLine>
      </configuration>
</plugin>

Thanks for all your responses and additional comments!