A quick script I use to truncate all entities registered in Doctrine:
$connection = $entityManager->getConnection();
$schemaManager = $connection->getSchemaManager();
$tables = $schemaManager->listTables();
$query = '';
foreach($tables as $table) {
$name = $table->getName();
$query .= 'TRUNCATE ' . $name . ';';
}
$connection->executeQuery($query, array(), array());