diff --git a/composer.json b/composer.json
index d621181c3..3b5d23822 100644
--- a/composer.json
+++ b/composer.json
@@ -29,7 +29,7 @@
         "codeigniter4/settings": "^2.1"
     },
     "require-dev": {
-        "boundwize/structarmed": "0.14.16",
+        "boundwize/structarmed": "0.15.1",
         "codeigniter/phpstan-codeigniter": "^2.0",
         "codeigniter4/devkit": "^1.3",
         "codeigniter4/framework": ">=4.3.5 <4.5.0 || ^4.5.1",
diff --git a/structarmed.php b/structarmed.php
index aab05444b..f4b4a47bd 100644
--- a/structarmed.php
+++ b/structarmed.php
@@ -5,8 +5,13 @@
 use Boundwize\StructArmed\Architecture;
 use Boundwize\StructArmed\Preset\Preset;
 use Boundwize\StructArmed\Preset\Presets\Psr4Preset;
+use Boundwize\StructArmed\Rule\Rules\Class_\MustBeFinalRule;
 
 return Architecture::define()
+    ->rule(
+        'tests.must_be_final',
+        new MustBeFinalRule(layer: 'tests'),
+    )
     ->skip([
         Psr4Preset::CLASSES_MUST_MATCH_COMPOSER => [
             __DIR__ . '/src/Database/Migrations',
@@ -14,6 +19,7 @@
     ])
     ->cacheDirectory(is_dir('/tmp') ? '/tmp/structarmed' : null)
     ->withPreset(Preset::PSR4())
+    ->layer('tests', __DIR__ . '/tests')
     ->layerPattern('Model', '/^CodeIgniter\\\\Shield\\\\.*Model$/')
     ->layerPattern('Controller', '/^CodeIgniter\\\\Shield\\\\Controllers\\\\.*$/')
     ->layerPattern('Config', '/^CodeIgniter\\\\Shield\\\\Config\\\\.*$/', '/^.*Services$/')
diff --git a/tests/_support/Config/Registrar.php b/tests/_support/Config/Registrar.php
index 3e9661c24..86a5e04e3 100644
--- a/tests/_support/Config/Registrar.php
+++ b/tests/_support/Config/Registrar.php
@@ -18,7 +18,7 @@
  *
  * Provides a basic registrar class for testing BaseConfig registration functions.
  */
-class Registrar
+final class Registrar
 {
     /**
      * DB config array for testing purposes.
@@ -27,7 +27,7 @@ class Registrar
      *
      * @psalm-suppress RedundantCondition
      */
-    protected static $dbConfig = [
+    private static $dbConfig = [
         'MySQLi' => [
             'DSN'      => '',
             'hostname' => '127.0.0.1',