public function testGetConnectionWithoutConnectionName()
 {
     $manager = new DatabaseManager($this->zibo);
     $manager->registerDriver('protocol', self::DRIVER_MOCK);
     $connectionName = 'test';
     $dsn = new Dsn('protocol://server/database');
     $manager->registerConnection($connectionName, $dsn);
     $connection = $manager->getConnection();
     $this->assertTrue($connection instanceof Driver, 'connection is not a Driver');
     $this->assertTrue($connection->isConnected(), 'connection is not connected');
 }