http://www.openbsd.org/images/rack2009.jpg
They run every version of OpenBSD in every machine they support, including 32bit SPARC, HP 300 and SGI. By running in all those machines they uncover subtle bugs that are made evident by architecture differences.
Also, please see http://anoncvs.estpak.ee/cgi-bin/cgit/openbsd-src/tree/regre...
Look, the whole OpenSSL debacle is the fact that OpenSSL has ONE programmer working on it reliably. LibreSSL now has 5x-10x the manpower that was working on OpenSSL--and that's STILL probably low by an order of magnitude.
Google should pledge 5 people to work on LibreSSL by itself. They clearly have them since one of their internal audits uncovered Heartbleed.
The thing is nobody in the companies actually cared until the NSA started spying on them.
Check out the 'snapshots' folder of any mirror. More info here: http://www.openbsd.org/ftp.html
What does "testing" mean in the LibreSSL/OpenSSL situation anyway? It compiles? A regression suite passes? Manual verification?