Class nameclass WC_Legacy_Cart{
   public function testfunction()
    {
    echo $variable_to_pass;

        $value_prova = apply_filters('get_value_from_function', $variable_to_pass);
        return $variable_to_pass;
    }
}

add_filter( 'woocommerce_calculated_total', 'change_calculated_total', 10, 2 );

function change_calculated_total( $total, $cart, $variable_to_pass ) {
    return $total + $variable_to_pass;

}