Travis project failing but not on own server

Travis project failing but not on own server

I'm pulling my hair out trying to fix the issues in my Travis CI build
failling. I can't seem to find out why it's working locally (probably a
configuration setting) but doesn't work on Travis CI.
My project is located at https://travis-ci.org/crazycodr/data-grouper on
Travis CI and the source is at https://github.com/crazycodr/data-grouper.
I have several issues in my build all related to
/src/CrazyCodr/Data/Grouper/GroupResult.php:447
But i don't see anything passed by reference over there so it's either a
configuration issues or something i just don't get!
Further more, if one could find out why i only have 65/68 tests being
run... I really don't get why i'm having this too, i check all my test
files and there are no test without an assertion or an @exceptedException
so i'm a bit clueless as to what is hapenning there... Note i have the
65/68 problem on both servers but the Reference error in the build is only
on Travis CI.