Issue #26332 BeforeOrderPaymentSaveObserver override payment insructions

Author: karyna-t

app/code/Magento/OfflinePayments/Observer/BeforeOrderPaymentSaveObserver.php

@@ -30,7 +30,8 @@ public function execute(\Magento\Framework\Event\Observer $observer)
             Banktransfer::PAYMENT_METHOD_BANKTRANSFER_CODE,
             Cashondelivery::PAYMENT_METHOD_CASHONDELIVERY_CODE
         ];
-        if (in_array($payment->getMethod(), $instructionMethods)) {
+        if (in_array($payment->getMethod(), $instructionMethods)
+            && empty($payment->getAdditionalInformation('instructions'))) {
             $payment->setAdditionalInformation(
                 'instructions',
                 $payment->getMethodInstance()->getInstructions()

app/code/Magento/OfflinePayments/Test/Unit/Observer/BeforeOrderPaymentSaveObserverTest.php

@@ -172,4 +172,24 @@ public function testBeforeOrderPaymentSaveWithOthers()
 
         $this->_model->execute($this->observer);
     }
+
+    /**
+     * @param string $methodCode
+     * @dataProvider dataProviderBeforeOrderPaymentSaveWithInstructions
+     */
+    public function testBeforeOrderPaymentSaveWithInstructionsAlreadySet($methodCode)
+    {
+        $this->payment
+            ->method('getMethod')
+            ->willReturn($methodCode);
+
+        $this->payment->expects(self::once())
+            ->method('getAdditionalInformation')
+            ->willReturn('Test');
+
+        $this->payment->expects(self::never())
+            ->method('setAdditionalInformation');
+
+        $this->_model->execute($this->observer);
+    }
 }