diff -u b/core/modules/config/lib/Drupal/config/Tests/ConfigExportImportUITest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigExportImportUITest.php
--- b/core/modules/config/lib/Drupal/config/Tests/ConfigExportImportUITest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigExportImportUITest.php
@@ -130,17 +130,17 @@
     $this->assertText('Changes have been made to your active configuration, which might be lost on the next import attempt. ' .
       'You can find and review the differences between snapshot and active/staging storage here');
 
-    $changedSlogan = $this->randomString(16);
+    $changed_slogan = $this->randomName(16);
 
     \Drupal::config('system.site')
-      ->set('slogan', $changedSlogan)
+      ->set('slogan', $changed_slogan)
       ->save();
 
     $this->clickLink('Compare snapshot and active/staging storage');
     $this->assertText('View changes between snapshot and active configuration');
     $this->assertText('system.site');
     $this->assertText('Active storage');
-    $this->assertText($changedSlogan, 'Changed slogan found on when viewing changes.');
+    $this->assertText($changed_slogan, "Changed slogan $changed_slogan found when viewing changes.");
     $this->clickLink('Compare snapshot with staging storage');
     $this->assertText('View changes between snapshot and staging configuration');