How can i delete options on plugin uninstallation?

Question

This will give you the option to register your unistall hook during plugin activation.

function myplugin_activation_callback(){
    register_uninstall_hook( __FILE__, 'myplugin_uninstall_callback' );
}
register_activation_hook( __FILE__, 'myplugin_activation_callback' );

function myplugin_uninstall_callback(){

    //Perform your uninstall operations here 
    delete_option('test_option');

}

However, the simplest way is to use an uninstall.php file with the following codes:

if (!defined('WP_UNINSTALL_PLUGIN')) {
    die;
}

//Perform your uninstall operations here 
delete_option('test_option');

It’s not recommended to use both at the same time.