C:\wamp\php>pear channel-discover pear.phpunit.de
Channel "pear.phpunit.de" is already initialized

C:\wamp\php>pear install phpunit/PHPUnit
Did not download optional dependencies: pear/Image_GraphViz, pear/Log, symfony/Y
AML, use --alldeps to download automatically
phpunit/PHPUnit requires PEAR Installer (version >= 1.8.1), installed version is
1.6.1
phpunit/PHPUnit can optionally use package "pear/Image_GraphViz" (version >= 1.2
.1)
phpunit/PHPUnit can optionally use package "pear/Log"
phpunit/PHPUnit can optionally use package "symfony/YAML" (version >= 1.0.2)
phpunit/PHPUnit can optionally use PHP extension "pdo_mysql"
phpunit/PHPUnit can optionally use PHP extension "soap"
phpunit/PHPUnit can optionally use PHP extension "xdebug" (version >= 2.0.5)
No valid packages found
install failed

pear install --alldeps phpunit/PHPUnit