When I run:
peardev install phpunit/PHPUnit
I get the following:
No releases available for package \"pear.phpunit.de/PHPUni
I'm a really newbie but hope to be of any help.
I just succeeded installing PHPUnit a moment ago.
My env. is Wamp2.1.
I don't know exactly how this works but it worked for me, so try this.
pear clear-cache then,
pear install -a -f phpunit/PHPUnit
Somewhere in the failing message, I saw something about cache so I used clear-cache.
It did some trick in installing process, I guess.
Good luck!