Assert class instances of collection items

modules/opd_daily_emails/src/DailyEmails.php

@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace Drupal\opd_daily_emails;
 
 use Drupal\node\NodeInterface;
+use Webmozart\Assert\Assert;
 
 final class DailyEmails implements \Countable {
 
@@ -14,6 +15,7 @@ final class DailyEmails implements \Countable {
   private function __construct(
     private array $emails,
   ) {
+    Assert::allIsInstanceOf($emails, NodeInterface::class);
   }
 
   public function count(): int {