add_action does not call the function

I want to add a custom field in the menu, therefore I am trying to use wp_nav_menu_item_custom_fields. I am using following code but it does not even call the function. I am adding it in a plugin, why is wrong in it?

add_action( 'wp_nav_menu_item_custom_fields', 'my_custom_fields', 10, 4);

function my_custom_fields( $item_id, $item, $depth, $args ) {
    var_dump("test test");
}