Classes should be final

tools/Phpat/ArchitectureTest.php

@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tools\Phpat;
+
+use PHPat\Selector\Selector;
+use PHPat\Test\Builder\Rule;
+use PHPat\Test\PHPat;
+
+final class ArchitectureTest {
+
+  public function test_classes_should_be_final(): Rule {
+    return PHPat::rule()
+      ->classes(
+        Selector::inNamespace(
+          namespace: '/^Drupal\\\\opd_\w+/',
+          regex: TRUE,
+        ),
+      )
+      ->excluding(Selector::isInterface())
+      ->shouldBeFinal();
+  }
+
+}