A while back I ran into a problem on a server where PHPUnit kept reporting "aborted" no matter what tests were run. That was a pretty annoying bug. I never did find out what the problem was as I moved onto other problems and chalked that error up to some undiagnosed weirdness on that particular server.
From time to time I would get asked on Twitter if I had ever solved the problem. My answer was always "no, and if you do solve it please let met know how you fixed it." Today, my friends, was the day.
Kudos to Damian Katz for coming up with a solution. Without digging deeper into it, I would imagine that you could alter the phpunit.xml file (if you are using one in your setup) to automatically use the -dzend.enable_gc=0 option every time you run a test.
How did he figure it out? He tracked down this bug that seemed to be displaying the exact behaviour that I had reported way back when. It seems odd that garbage collection would cause this problem, but perhaps it was a perfect storm of lots of small tests causing over-active garbage collection which in turn causes the PHP interpreter to abort whatever it is running.
This is another case where I would love someone with knowledge of PHP internals to try and explain why it is happening.