If you want to use doctrine:fixtures:load, you can use the --append option to avoid the user confirmation. Since you are recreating the database every time, purging is unnecessary. I used to use doctrine fixtures alone for testing, but have since switched to using fixtures & LiipFunctionalTestBundle to avoid DRY. This bundle makes fixtures easier to manage.
EDIT: David Jacquel’s answer is the correct one for loading Doctrine Fixtures:
doctrine:fixtures:load --no-interaction
or
doctrine:fixtures:load -n