core/modules/comment/src/Tests/CommentTestBase.php | 17 ++++++++++++++++-
 core/modules/system/system.install                 |  6 +++---
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/core/modules/comment/src/Tests/CommentTestBase.php b/core/modules/comment/src/Tests/CommentTestBase.php
index f78a8bd..75efbd4 100644
--- a/core/modules/comment/src/Tests/CommentTestBase.php
+++ b/core/modules/comment/src/Tests/CommentTestBase.php
@@ -188,7 +188,22 @@ public function postComment($entity, $comment, $subject = '', $contact = NULL, $
    */
   function commentExists(CommentInterface $comment = NULL, $reply = FALSE) {
     if ($comment) {
-      return (bool) $this->cssSelect('.comment-wrapper ' . ($reply ? '.indented ' : '') . '#comment-' . $comment->id());
+      $comment_element = $this->cssSelect('.comment-wrapper ' . ($reply ? '.indented ' : '') . '#comment-' . $comment->id() . ' ~ article');
+      if (empty($comment_element)) {
+        return FALSE;
+      }
+
+      $comment_title = $comment_element[0]->xpath('div/h3/a');
+      if (empty($comment_title) || ((string)$comment_title[0]) !== $comment->getSubject()) {
+        return FALSE;
+      }
+
+      $comment_body = $comment_element[0]->xpath('div/div/p');
+      if (empty($comment_body) || ((string)$comment_body[0]) !== $comment->comment_body->value) {
+        return FALSE;
+      }
+
+      return TRUE;
     }
     else {
       return FALSE;
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index 2f155b9..c59765e 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -1468,16 +1468,16 @@ function system_update_8005() {
 
       default:
         $custom_themes_installed = TRUE;
-        $name = sprintf('block.block.%s_local_actions', $theme_name);
+        $name = 'block.block.' . $theme_name . '_local_actions';
         $values = [
-          'id' => sprintf('%s_local_actions', $theme_name),
+          'id' => $theme_name . '_local_actions',
           'weight' => -10,
         ] + $local_actions_default_settings;
         _system_update_create_block($name, $theme_name, $values);
 
         $name = sprintf('block.block.%s_local_tasks', $theme_name);
         $values = [
-          'id' => sprintf('%s_local_tasks', $theme_name),
+          'id' => $theme_name . '_local_tasks',
           'weight' => -20,
         ] + $tabs_default_settings;
         _system_update_create_block($name, $theme_name, $values);