I used composer to install the phpunit dependency, so if you want the working app you should have a composer.phar file available (you can get one at https://getcomposer.org/download/)
move to the root of he project and
composer install
(note I assume you have PHP >=5.3)
to run the application simply run
php export_payment_dates.php
You can run the whole testsuite with
vendor/bin/phpunit -c . --testdox
I named my test so that running test with the --testdox flag provides best output.