See https://docs.docker.com/install/
Install PHPUnit and other development dependencies via composer:
composer install
docker-compose up --build
docker exec -it -w /var/www/html/wp-content/plugins/event-organiser eventorg_php ./vendor/bin/phpunit
docker exec -it -w /var/www/html/wp-content/plugins/event-organiser eventorg_php mkdir failed-scenerios
docker exec -it -w /var/www/html/wp-content/plugins/event-organiser eventorg_php ./vendor/bin/behat