Documentation :

emblem-notice-24.pngThis new major version requires PHP ≥ 7.0 and is not backward compatible with previous version, so the package is designed to be installed beside version 5.

Installation, Fedora:

dnf --enablerepo=remi install phpunit6

Installation, Enterprise Linux:

yum --enablerepo=remi install phpunit6 php-phpunit-dbunit3

Notice: this tool is an essential component of PHP QA in Fedora. I quickly plan an update in Fedora 26, as soon as php-sebastian-diff2 will be approved (review #1478358).