ENGCOM-1382: For MSI-377: fix test fixture and mark return processor as @api #14842

 - Merge Pull Request #14842 from seruymt/magento2:MSI-377
 - Merged commits:
   1. 2109eb6

Author: magento-engcom-team

app/code/Magento/SalesInventory/Model/Order/ReturnProcessor.php

@@ -10,6 +10,8 @@
 
 /**
  * Class ReturnProcessor
+ *
+ * @api
  */
 class ReturnProcessor
 {

dev/tests/integration/testsuite/Magento/Sales/_files/order_with_shipping_and_invoice.php

@@ -3,6 +3,9 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+
+use Magento\Sales\Model\Order\ShipmentFactory;
+
 require 'order.php';
 
 $objectManager = \Magento\TestFramework\Helper\Bootstrap::getObjectManager();
@@ -36,4 +39,10 @@
 
 $order->setIsInProcess(true);
 
-$transaction->addObject($invoice)->addObject($order)->save();
+$items = [];
+foreach ($order->getItems() as $orderItem) {
+    $items[$orderItem->getId()] = $orderItem->getQtyOrdered();
+}
+$shipment = $objectManager->get(ShipmentFactory::class)->create($order, $items);
+
+$transaction->addObject($invoice)->addObject($shipment)->addObject($order)->save();