diff --git a/app/Services/OAuth2/ApiScopeGroupService.php b/app/Services/OAuth2/ApiScopeGroupService.php
index 66b8ac65..e757a72c 100644
--- a/app/Services/OAuth2/ApiScopeGroupService.php
+++ b/app/Services/OAuth2/ApiScopeGroupService.php
@@ -14,6 +14,7 @@
 use App\Models\OAuth2\Factories\ApiScopeGroupFactory;
 use Auth\Repositories\IUserRepository;
 use models\exceptions\EntityNotFoundException;
+use models\exceptions\ValidationException;
 use models\utils\IEntity;
 use OAuth2\Exceptions\InvalidApiScopeGroup;
 use OAuth2\Repositories\IApiScopeRepository;
@@ -100,7 +101,7 @@ public function update(int $id, array $payload):IEntity
                 $former_group = $this->repository->getByName($payload['name']);
                 if(!is_null($former_group) && $former_group->getId() != $id)
                 {
-                    throw new InvalidApiScopeGroup(sprintf('there is already another api scope group name (%s).', $payload['name']));
+                    throw new ValidationException(sprintf('there is already another api scope group name (%s).', $payload['name']));
                 }
             }
 
@@ -144,7 +145,7 @@ public function create(array $payload):IEntity
 
             if(!is_null($former_group))
             {
-                throw new InvalidApiScopeGroup(sprintf('there is already another api scope group name (%s).', $name));
+                throw new ValidationException(sprintf('there is already another api scope group name (%s).', $name));
             }
             $group  = ApiScopeGroupFactory::build($payload);
             $scopes = $payload['scopes'];
diff --git a/tests/unit/ApiScopeGroupServiceTest.php b/tests/unit/ApiScopeGroupServiceTest.php
new file mode 100644
index 00000000..43968fa1
--- /dev/null
+++ b/tests/unit/ApiScopeGroupServiceTest.php
@@ -0,0 +1,67 @@
+<?php namespace Tests\unit;
+
+/**
+ * Copyright 2026 OpenStack Foundation
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+use LaravelDoctrine\ORM\Facades\EntityManager;
+use models\exceptions\ValidationException;
+use Models\OAuth2\ApiScopeGroup;
+use OAuth2\Services\IApiScopeGroupService;
+use Tests\BrowserKitTestCase;
+
+/**
+ * Class ApiScopeGroupServiceTest
+ * A duplicated group name must surface as a ValidationException (HTTP 412 in
+ * ApiScopeGroupController), not as an unhandled exception (HTTP 500).
+ * @package Tests\unit
+ */
+class ApiScopeGroupServiceTest extends BrowserKitTestCase
+{
+    private function persistGroup(string $name): ApiScopeGroup
+    {
+        $group = new ApiScopeGroup();
+        $group->setName($name);
+        $group->setActive(true);
+        $group->setDescription('test description');
+        EntityManager::persist($group);
+        EntityManager::flush();
+        return $group;
+    }
+
+    public function testUpdateWithNameUsedByAnotherGroupThrowsValidationException()
+    {
+        $suffix = uniqid();
+        $this->persistGroup("group_a_$suffix");
+        $group_b = $this->persistGroup("group_b_$suffix");
+
+        $this->expectException(ValidationException::class);
+        $this->expectExceptionMessage("group_a_$suffix");
+
+        app(IApiScopeGroupService::class)->update($group_b->getId(), ['name' => "group_a_$suffix"]);
+    }
+
+    public function testCreateWithExistingNameThrowsValidationException()
+    {
+        $name = 'group_dup_' . uniqid();
+        $this->persistGroup($name);
+
+        $this->expectException(ValidationException::class);
+        $this->expectExceptionMessage($name);
+
+        app(IApiScopeGroupService::class)->create([
+            'name'   => $name,
+            'scopes' => '',
+            'users'  => '',
+        ]);
+    }
+}