The tests fail with a SMP R14B01 emulator running on Linux:
==> erlzmq2 (eunit)
Fatal error in erl_drv_mutex_destroy(): Device or resource busy 
make: *** [test] Aborted
What's the ulimit -n?
$ ulimit -n
Apparently we didn't have the right commit in place for the last fix. Can you re-pull please?
That commit fixed this issue.
Thanks for the report !