MAGETWO-71771: imposible perform full refund for Order Paid with PayPal Payments Standard

- Use repository to save Order model in integration test

Author: danielrenaud

dev/tests/integration/testsuite/Magento/Paypal/Model/Api/NvpTest.php

@@ -125,7 +125,6 @@ public function testRequestTotalsAndLineItemsWithFPT()
      */
     public function testCallRefundTransaction()
     {
-        $this->assertTrue(true);
         /** @var \Magento\Sales\Model\Order $order */
         $order = $this->objectManager->create(\Magento\Sales\Model\Order::class);
         $order->loadByIncrementId('100000001');

dev/tests/integration/testsuite/Magento/Paypal/_files/order_express_with_tax.php

@@ -4,8 +4,15 @@
  * See COPYING.txt for license details.
  */
 
+use Magento\Framework\ObjectManagerInterface;
+use Magento\Sales\Model\OrderRepository;
+use Magento\TestFramework\Helper\Bootstrap;
+
 require __DIR__ . '/order_express.php';
 
+/** @var ObjectManagerInterface $objectManager */
+$objectManager = Bootstrap::getObjectManager();
+
 $subTotal = 121;
 $taxRate = .0825;
 $taxAmount = $subTotal * $taxRate;
@@ -18,4 +25,6 @@
 $order->setBaseGrandTotal($totalAmount);
 $order->setTaxAmount($taxAmount);
 
-$order->save();
+/** @var OrderRepository $orderRepository */
+$orderRepository = $objectManager->get(OrderRepository::class);
+$orderRepository->save($order);