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.