Get Order Ids in a WooCommerce Plugin - php

Question

Trying to update order post meta in testmain(), I can update it when I manually assign a order id, but struggling to figure out how to get order ids, where am I going wrong?
<?php
/**
* Plugin Name: MyTestPlugin
*/
defined('ABSPATH') or die('Bye');
if (in_array( 'woocommerce/woocommerce.php', apply_filters('active_plugins', get_option('active_plugins')))){
if (! wp_next_scheduled('my_test_cron')){
wp_schedule_event(time(), 'hourly', 'my_test_cron');
}
if (! class_exists('MyTest')) :
class MyTest {
public function __construct(){
add_filter('manage_edit-shop_order_columns', array($this, 'my_manage_edit_shop_order_columns'));
add_action('manage_posts_custom_column', array($this, 'my_manage_posts_custom_column'));
add_action('my_test_cron', array($this, 'testmain'));
$this->pluginPath = dirname(__FILE__);
}
public function testmain(){
// $the_id = '9001'; // <-- ORDER ID
$the_data = 'Sample Data';
update_post_meta(get_the_ID(), '_my_test', $the_data);
}
public function my_manage_edit_shop_order_columns($col_th){
return wp_parse_args(array('_my_test' => 'My Test'), $col_th);
}
public function my_manage_posts_custom_column($column_id){
if($column_id == '_my_test')
echo get_post_meta(get_the_ID(), '_my_test', true);
}
}
$MyTest = new MyTest();
endif;
}

Answer 1

I was going the wrong way about trying to update the meta data.
Solved.
public function testmain(){
$args = array(
'limit' => -1,
);
$orders = wc_get_orders( $args );
foreach ($orders as $order){
$order->update_meta_data('_my_test', 'Sample Data');
$order->save();
}
}