The preinstalled version of PHPunit is incompatible with PHP


The PHP 7.0 job pre-installs PHPUnit 7.5, which requires PHP 7.1+.
The PHP 7.1 job pre-installs PHPUnit 8.0, which requires PHP 7.2+.


This is also happening on DokuWiki. It looks like while the (old) Trusty one was working, the Xenial default upgrade makes this issue arise:

For anyone arriving here from Google - you are probably using phpunit in your scripts.

Change it to ./vendor/bin/phpunit to use the version that Composer installs and you should be all set.