ENGCOM-4635: Fixed assignment of the guest customer to the guest group when 'Automatic Assignment by VAT ID' is enabled #22091

 - Merge Pull Request #22091 from vovayatsyuk/magento2:fix-customer-group-assignment-for-empty-vat
 - Merged commits:
   1. b00402d
   2. b4c6158

Author: magento-engcom-team

app/code/Magento/Quote/Observer/Frontend/Quote/Address/CollectTotalsObserver.php

@@ -7,6 +7,11 @@
 
 use Magento\Framework\Event\ObserverInterface;
 
+/**
+ * Handle customer VAT number on collect_totals_before event of quote address.
+ *
+ * @SuppressWarnings(PHPMD.CookieAndSessionMisuse)
+ */
 class CollectTotalsObserver implements ObserverInterface
 {
     /**

app/code/Magento/Quote/Test/Unit/Observer/Frontend/Quote/Address/CollectTotalsObserverTest.php

@@ -199,7 +199,7 @@ public function testDispatchWithCustomerCountryNotInEUAndNotLoggedCustomerInGrou
             ->method('getNotLoggedInGroup')
             ->will($this->returnValue($this->groupInterfaceMock));
         $this->groupInterfaceMock->expects($this->once())
-            ->method('getId')->will($this->returnValue(0));
+            ->method('getId')->will($this->returnValue(null));
         $this->vatValidatorMock->expects($this->once())
             ->method('isEnabled')
             ->with($this->quoteAddressMock, $this->storeId)
@@ -220,9 +220,6 @@ public function testDispatchWithCustomerCountryNotInEUAndNotLoggedCustomerInGrou
             $this->returnValue(false)
         );
 
-        $groupMock = $this->getMockBuilder(\Magento\Customer\Api\Data\GroupInterface::class)
-            ->disableOriginalConstructor()
-            ->getMock();
         $this->customerMock->expects($this->once())->method('getId')->will($this->returnValue(null));
 
         /** Assertions */