如何安装phpunit？
我阅读了文档https://github.com/sebastianbergmann/phpunit,但有一个错误:
>pear upgrade PEAR
Nothing to upgrade
>pear config-set auto_discover 1
config-set succeeded
>pear install pear.phpunit.de/PHPUnit
No releases available for package "pear.phpunit.de/PHPUnit"
install failed
我该如何解决这个错误？