Michal Suchanek wrote:
>  Setting up VMs for Windows or some BSDs should be easy. However, OS X
>  cannot be virtualized so only people with apple hardware running
>  that thing can test.
Running OS X in a VM works well, although it's a rather slow and the 
legality is fuzzy:
    http://wiki.osx86project.org/wiki/index.php/Vmware_how_to

>  There is the possibility to test on Darwin but it would be probably
>  hard to set up environment identical to current OS X.
Agreed, it'd be best to use a full copy of OS X to properly simulate 
this. Most Rails developers use OS X, so it's important to support that 
platform.

>  There seem to be many people with OS X desktops but i am not sure
>  there are many OS X servers free to run some untested code.
True. We can either ask for donations of a machine or run this off a 
service similar to http://www.macminicolo.net/

>  Perhaps some best effort parallel execution like Seti@home could make
>  things easier for exotic platforms.
Perl uses a fully distributed system for testing CPAN modules 
(conceptually similar to Gems). Folks can download an agent and it'll 
run tests on various modules. This allows those running exotic platforms 
like A/UX, z390s and HP/UX to contribute their results. We may be able 
to reuse their system.

-igal