Step 1: Test current behavior with non-unique alter types

core/modules/system/tests/modules/HookOrder/aaa_hook_order_test/src/Hook/AAlterHooks.php

@@ -5,6 +5,8 @@
 namespace Drupal\aaa_hook_order_test\Hook;
 
 use Drupal\Core\Hook\Attribute\Hook;
+use Drupal\Core\Hook\Attribute\ReorderHook;
+use Drupal\Core\Hook\Order\Order;
 use Drupal\Core\Hook\Order\OrderAfter;
 
 /**
@@ -26,4 +28,34 @@ public function testSubtypeAlter(array &$calls): void {
     $calls[] = __METHOD__;
   }
 
+  #[Hook('test_tomato_alter')]
+  #[Hook('test_tomato_alter')]
+  public function testTomatoTomatoAlter(array &$calls): void {
+    $calls[] = __METHOD__;
+  }
+
+  #[Hook('test_apple_alter')]
+  #[Hook('test_orange_alter')]
+  public function testAppleOrangeAlter(array &$calls): void {
+    $calls[] = __METHOD__;
+  }
+
+  #[Hook('test_moth_alter')]
+  #[Hook('test_butterfly_alter', module: 'bbb_hook_order_test')]
+  public function testMothButterflyAlter(array &$calls): void {
+    $calls[] = __METHOD__;
+  }
+
+  #[ReorderHook('test_summer_alter', self::class, 'testSummerAlter', Order::Last)]
+  #[ReorderHook('test_winter_alter', self::class, 'testWinterAlter', Order::Last)]
+  #[Hook('test_summer_alter')]
+  public function testSummerAlter(array &$calls): void {
+    $calls[] = __METHOD__;
+  }
+
+  #[Hook('test_winter_alter')]
+  public function testWinterAlter(array &$calls): void {
+    $calls[] = __METHOD__;
+  }
+
 }