- Simplifies code that prepares subscriber custom field data for

creation/update
- Updates tests

tests/unit/Subscribers/ImportExport/Import/ImportTest.php

@@ -279,18 +279,18 @@ class ImportTest extends MailPoetTest {
       $this->subscriber_fields,
       false
     );
-    $db_subscribers = Helpers::arrayColumn(
+    $db_subscribers_ids = Helpers::arrayColumn(
       Subscriber::selectMany(
         array(
           'id',
           'email'
         ))
         ->findArray(),
-      'email', 'id'
+      'id'
     );
     $this->import->createOrUpdateCustomFields(
       'create',
-      $db_subscribers,
+      $db_subscribers_ids,
       $subscribers_data,
       $this->subscriber_custom_fields
     );
@@ -301,7 +301,7 @@ class ImportTest extends MailPoetTest {
     $subscribers_data[$custom_field][1] = 'Rio';
     $this->import->createOrUpdateCustomFields(
       'update',
-      $db_subscribers,
+      $db_subscribers_ids,
       $subscribers_data,
       $this->subscriber_custom_fields
     );