diff -u b/core/modules/rest/tests/src/Functional/EntityResource/Item/ItemResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/Item/ItemResourceTestBase.php
--- b/core/modules/rest/tests/src/Functional/EntityResource/Item/ItemResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Item/ItemResourceTestBase.php
@@ -65,12 +65,11 @@
     $feed->save();
 
     // Create a "Llama" item.
-    $item = Item::create([
-      'fid' => $feed->id(),
-      'title' => t('Llama'),
-      'link' => 'https://www.drupal.org/',
-    ]);
-    $item->setPostedTime(123456789)
+    $item = Item::create();
+    $item->setTitle('Llama')
+      ->setFeedId($feed->id())
+      ->setLink('https://www.drupal.org/')
+      ->setPostedTime(123456789)
       ->save();
 
     return $item;
@@ -98,7 +97,7 @@
           'target_id' => 1,
           'target_type' => 'aggregator_feed',
           'target_uuid' => $feed->uuid(),
-          'url' => $feed->toUrl()->toString(),
+          'url' => '/aggregator/sources/1',
         ],
       ],
       'title' => [
@@ -129,7 +128,7 @@
     return [
       'fid' => [
         [
-          'target_id' => Feed::load(1)->id(),
+          'target_id' => 1,
         ],
       ],
       'title' => [