Run composer install command from root directory of the project.
composer install
Run phpunit command from root directory of the project.
phpunit
$tripSorter = new TripSorter();
$sortedBoardingCards = $tripSorter->addBoardingCard($airplaneCard1)
->addBoardingCard($airplaneCard2)
->addBoardingCard($busCard)
->addBoardingCard($trainCard)
->sortBoardingCards()
->getSortedBoardingCards();