diff --git a/core/modules/comment/tests/src/Kernel/CommentOrphanTest.php b/core/modules/comment/tests/src/Kernel/CommentOrphanTest.php
new file mode 100644
index 0000000000..2adb118319
--- /dev/null
+++ b/core/modules/comment/tests/src/Kernel/CommentOrphanTest.php
@@ -0,0 +1,178 @@
+<?php
+
+namespace Drupal\Tests\rdf\Kernel;
+
+use Drupal\Core\Datetime\Entity\DateFormat;
+use Drupal\KernelTests\Core\Entity\EntityKernelTestBase;
+use Drupal\Tests\EntityViewTrait;
+use Drupal\field\Entity\FieldStorageConfig;
+
+/**
+ * Tests loading and rendering orphan comments.
+ *
+ * @group comment
+ */
+class CommentOrphanTest extends EntityKernelTestBase {
+
+  use EntityViewTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['comment', 'node'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->installEntitySchema('date_format');
+    $this->installEntitySchema('comment');
+    $this->installSchema('comment', ['comment_entity_statistics']);
+  }
+
+  /**
+   * Test loading/deleting/rendering orphaned comments.
+   *
+   * @dataProvider providerTestOrphan
+   */
+  public function testOrphan($property) {
+
+    DateFormat::create([
+      'id' => 'fallback',
+      'label' => 'Fallback',
+      'pattern' => 'Y-m-d',
+    ])->save();
+
+    $comment_storage = $this->entityTypeManager->getStorage('comment');
+    $node_storage = $this->entityTypeManager->getStorage('node');
+
+    // Create a page node type.
+    $this->entityTypeManager->getStorage('node_type')->create([
+      'type' => 'page',
+      'name' => 'page',
+    ])->save();
+
+    $node = $node_storage->create([
+      'type' => 'page',
+      'title' => 'test',
+    ]);
+    $node->save();
+
+    // Create comment field.
+    $this->entityTypeManager->getStorage('field_storage_config')->create([
+      'type' => 'text_long',
+      'entity_type' => 'node',
+      'field_name' => 'comment',
+    ])->save();
+
+    // Add comment field to page content.
+    $this->entityTypeManager->getStorage('field_config')->create([
+      'field_storage' => FieldStorageConfig::loadByName('node', 'comment'),
+      'entity_type' => 'node',
+      'bundle' => 'page',
+      'label' => 'Comment',
+    ])->save();
+
+    // Make two comments
+    $comment1 = $comment_storage->create([
+      'field_name' => 'comment',
+      'comment_body' => 'test',
+      'entity_id' => $node->id(),
+      'entity_type' => 'node',
+      'comment_type' => 'default',
+    ])->save();
+
+    $comment_storage->create([
+      'field_name' => 'comment',
+      'comment_body' => 'test',
+      'entity_id' => $node->id(),
+      'entity_type' => 'node',
+      'comment_type' => 'default',
+      'pid' => $comment1,
+    ])->save();
+
+    // Render the comments.
+    $renderer = \Drupal::service('renderer');
+    $comments = $comment_storage->loadMultiple();
+    foreach ($comments as $comment) {
+      $built = $this->buildEntityView($comment, 'full', NULL);
+      $renderer->renderPlain($built);
+    }
+
+    // Make comment 2 an orphan.
+    $this->orphanComments([2], [$property]);
+    $comment_storage->resetCache();
+    $node_storage->resetCache();
+
+    // Render the comments with an orphan comment.
+    $comments = $comment_storage->loadMultiple();
+    foreach ($comments as $comment) {
+      $built = $this->buildEntityView($comment, 'full', NULL);
+      $renderer->renderPlain($built);
+    }
+
+    $node = $node_storage->load($node->id());
+    $built = $this->buildEntityView($node, 'full', NULL);
+    $renderer->renderPlain($built);
+  }
+
+  /**
+   * Creates orphaned comments.
+   *
+   * Intentionally makes reference data (commented entity, parent comment,
+   * author) invalid, in the SQL storage backend.
+   *
+   * @param array $comment_ids
+   *   IDs of comments to orphan. If empty, invalidate the most recent comment.
+   * @param array $fields
+   *   Names of fields to change. Allowed values: 'pid', 'entity_id', 'uid'. If
+   *   empty, all fields will be changed.
+   */
+  public function orphanComments(array $comment_ids = [], array $fields = []) {
+
+    $database = \Drupal::database();
+    // Get the maximum parent/author and set it one higher; this emulates
+    // a parent/author which has been deleted after creating.
+    $query = $database->select('comment_field_data', 'c');
+    $query->addExpression('MAX(cid)', 'cid_max');
+    $query->addExpression('MAX(pid)', 'pid_max');
+    $query->addExpression('MAX(uid)', 'uid_max');
+    $query->addExpression('MAX(entity_id)', 'entity_id_max');
+    $row = $query->execute()->fetchObject();
+    if (!isset($row->pid_max) && isset($row->cid_max)) {
+      $row->pid_max = $row->cid_max;
+    }
+
+    if (empty($comment_ids) && isset($row->cid_max)) {
+      $comment_ids = [$row->cid_max];
+    }
+
+    if (!empty($comment_ids)) {
+      $update_values = [
+        'entity_id' => $row->entity_id_max + 1,
+        'pid' => $row->cid_max + 1,
+        'uid' => $row->uid_max + 1,
+      ];
+      if ($fields) {
+        $update_values = array_intersect_key($update_values, array_flip($fields));
+      }
+      $database->update('comment_field_data')
+        ->fields($update_values)
+        ->condition('cid', $comment_ids)
+        ->execute();
+    }
+  }
+
+  /**
+   * Provides test data for testOrphan.
+   */
+  public function providerTestOrphan() {
+    return [
+      ['entity_id'],
+      ['uid'],
+      ['pid'],
+    ];
+  }
+
+}