After some tweaking I managed to make my test work on Windows as well. I added the test to S29-os/system.t with commit https://github.com/perl6/roast/commit/0f4b5b6b49
The error was not fixed for Parrot, but since support for Parrot was suspended with Rakudo Star Release 2015.02, I'm closing this ticket as 'resolved'. I'll add the ticket to a list of closed ticket living in the mu repository: https://github.com/perl6/mu/blob/master/misc/rt.perl.org/tickets_closed_parrot_only.txt. In case support for Parrot will be restored in some future release the listed tickets can be checked and re-opened as appropriate.
