Unit tests only fail when run by maven

I'm currently facing the problem that my unit tests are passing when run by eclipse but failing when run by maven.

This is the repository (+ pom.xml): http://ift.tt/29pBGmq

Here is the build log: http://ift.tt/29wpIu1

This is the output of mvn -v:

Apache Maven 3.3.9 (NON-CANONICAL_2015-11-23T13:17:27+03:00_root; 2015-11-   23T11:17:27+01:00)
Maven home: /opt/maven
Java version: 1.8.0_92, vendor: Oracle Corporation
Java home: /usr/lib/jvm/java-8-openjdk/jre
Default locale: de_DE, platform encoding: UTF-8
OS name: "linux", version: "4.6.3-1-arch", arch: "amd64", family: "unix"

I've tried to change my java version from 1.7 to 1.6 but this didn't help.

I appreciate any suggestions

Best, Thorsten