It seems like your version installed globally does not meet the minimal required version. Try to run
phpunit --version
I bet you will get something like 5.1
. The php artisan dusk
command uses different version which is located in vendor/bin/phpunit
. So, you are also able to use this version instead. Just type:
vendor/bin/phpunit
instead of phpunit
. You have to upgrade your global phpunit version if it works.