diff --git a/core/modules/aggregator/tests/src/Unit/Plugin/AggregatorPluginSettingsBaseTest.php b/core/modules/aggregator/tests/src/Unit/Plugin/AggregatorPluginSettingsBaseTest.php
index 56c0339..e5666f7 100644
--- a/core/modules/aggregator/tests/src/Unit/Plugin/AggregatorPluginSettingsBaseTest.php
+++ b/core/modules/aggregator/tests/src/Unit/Plugin/AggregatorPluginSettingsBaseTest.php
@@ -55,7 +55,7 @@ protected function setUp() {
         ->will($this->returnValue(['aggregator_test' => ['title' => '', 'description' => '']]));
     }
 
-    $this->settingsForm = new SettingsForm(
+    $this->settingsForm = new TestSettingsForm(
       $this->configFactory,
       $this->managers['fetcher'],
       $this->managers['parser'],
@@ -105,10 +105,12 @@ public function testSettingsForm() {
 
 }
 
-// @todo Delete after https://www.drupal.org/node/2278383 is in.
-namespace Drupal\Core\Form;
+class TestSettingsForm extends SettingsForm {
 
-if (!function_exists('drupal_set_message')) {
-  function drupal_set_message() {
+  function messenger() {
+    return new class() {
+      public function addStatus() {
+      }
+    };
   }
 }