Download the most recent PHPUnit PHAR from https://phar.phpunit.de

Move it to /usr/local/bin

mv /Users/davidvandertuijn/Downloads/phpunit-9.5.5.phar /usr/local/bin/phpunit-9.5.5.phar

Make it executable

chmod +x /usr/local/bin/phpunit-9.5.5.phar

Make a symbolic link

ln -s /usr/local/bin/phpunit-9.5.5.phar /usr/local/bin/phpunit

Check the version

phpunit -—version

PHPUnit 9.5.5 by Sebastian Bergmann and contributors.