try 

    $installer->addAttribute('customer', 'testveri', array(
        'label' => 'Working?',
        'input' => 'select',
        'type'  => 'int',
        'forms' => array('adminhtml_customer'),
        'source'  => 'eav/entity_attribute_source_boolean',
        'required' => 0,
        'user_defined' => 0,
    ));