diff --git a/composer.json b/composer.json
index 80a601694..262b08f9b 100644
--- a/composer.json
+++ b/composer.json
@@ -65,7 +65,7 @@
     "qtism/qtism": ">=0.28.3",
     "oat-sa/generis" : ">=15.22",
     "oat-sa/tao-core": ">=53.0.0",
-    "oat-sa/extension-tao-item" : ">=12.0.0",
+    "oat-sa/extension-tao-item" : ">=12.1.0",
     "oat-sa/extension-tao-itemqti" : ">=30.0.0",
     "oat-sa/extension-tao-test" : ">=16.0.0",
     "oat-sa/extension-tao-delivery" : ">=15.0.0",
diff --git a/models/classes/class.QtiTestService.php b/models/classes/class.QtiTestService.php
index a200b4129..0f179b1bb 100644
--- a/models/classes/class.QtiTestService.php
+++ b/models/classes/class.QtiTestService.php
@@ -15,8 +15,7 @@
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  *
- * Copyright (c) 2013-2018 (original work) Open Assessment Technologies SA (under the project TAO-PRODUCT);
- *
+ * Copyright (c) 2013-2023 (original work) Open Assessment Technologies SA (under the project TAO-PRODUCT);
  */
 
 use League\Flysystem\FileExistsException;
@@ -26,7 +25,7 @@
 use oat\tao\model\resources\ResourceAccessDeniedException;
 use oat\tao\model\resources\SecureResourceServiceInterface;
 use oat\tao\model\TaoOntology;
-use oat\taoBackOffice\model\tree\TreeService;
+use oat\taoItems\model\Command\DeleteItemCommand;
 use oat\taoQtiItem\model\qti\ImportService;
 use oat\taoQtiItem\model\qti\metadata\importer\MetadataImporter;
 use oat\taoQtiItem\model\qti\metadata\MetadataGuardianResource;
@@ -40,6 +39,7 @@
 use oat\taoQtiTest\models\render\QtiPackageImportPreprocessing;
 use oat\taoQtiTest\models\test\AssessmentTestXmlFactory;
 use oat\taoTests\models\event\TestUpdatedEvent;
+use Psr\Container\ContainerInterface;
 use qtism\common\utils\Format;
 use qtism\data\AssessmentItemRef;
 use qtism\data\QtiComponentCollection;
@@ -57,7 +57,6 @@
  * @author Bertrand Chevrier <bertrand@taotesting.com>
  * @author Jerome Bogaerts <jerome@taotesting.com>
  * @package taoQtiTest
-
  */
 class taoQtiTest_models_classes_QtiTestService extends TestService
 {
@@ -348,7 +347,6 @@ public function importMultipleTests(
         bool $overwriteTest = false,
         ?string $itemClassUri = null
     ) {
-
         $testClass = $targetClass;
         $report = new common_report_Report(common_report_Report::TYPE_INFO);
         $validPackage = false;
@@ -866,6 +864,9 @@ protected function importTest(
         return $report;
     }
 
+    /**
+     * @throws common_Exception
+     */
     private function deleteTestsFromClassByLabel(
         string $testLabel,
         string $itemsClassLabel,
@@ -873,19 +874,14 @@ private function deleteTestsFromClassByLabel(
         core_kernel_classes_Class $itemClass
     ): void {
         $testService = $this->getTestService();
-        $itemTreeService = $this->getItemTreeService();
+
+        $this->deleteItemSubclassesByLabel($itemClass, $itemsClassLabel);
 
         foreach ($testClass->getInstances() as $testInstance) {
             if ($testInstance->getLabel() === $testLabel) {
                 $testService->deleteTest($testInstance);
             }
         }
-
-        foreach ($itemClass->getSubClasses() as $subClass) {
-            if ($subClass->getLabel() === $itemsClassLabel) {
-                $itemTreeService->deleteClass($subClass);
-            }
-        }
     }
 
     /**
@@ -1446,21 +1442,42 @@ private function verifyItemPermissions(core_kernel_classes_Resource $oldTest, st
         $this->getSecureResourceService()->validatePermissions($ids, ['READ']);
     }
 
-    /**
-     * @return QtiPackageImportPreprocessing
-     */
-    private function getQtiPackageImportPreprocessing()
+    private function deleteItemSubclassesByLabel(
+        core_kernel_classes_Class $root,
+        string $label
+    ): void {
+        $itemTreeService = $this->getItemTreeService();
+
+        foreach ($root->getSubClasses() as $subClass) {
+            if ($subClass->getLabel() !== $label) {
+                continue;
+            }
+
+            foreach ($subClass->getInstances(true) as $instance) {
+                $itemTreeService->delete(new DeleteItemCommand($instance, true));
+            }
+
+            $itemTreeService->deleteClass($subClass);
+        }
+    }
+
+    private function getQtiPackageImportPreprocessing(): QtiPackageImportPreprocessing
     {
-        return $this->getServiceLocator()->get(QtiPackageImportPreprocessing::SERVICE_ID);
+        return $this->getPsrContainer()->get(QtiPackageImportPreprocessing::SERVICE_ID);
     }
 
     private function getItemTreeService(): taoItems_models_classes_ItemsService
     {
-        return taoItems_models_classes_ItemsService::singleton();
+        return $this->getPsrContainer()->get(taoItems_models_classes_ItemsService::class);
     }
 
     private function getTestService(): taoTests_models_classes_TestsService
     {
-        return taoTests_models_classes_TestsService::singleton();
+        return $this->getPsrContainer()->get(taoTests_models_classes_TestsService::class);
+    }
+
+    private function getPsrContainer(): ContainerInterface
+    {
+        return $this->getServiceLocator()->getContainer();
     }
 }
diff --git a/test/unit/models/classes/xml/XmlEditorTest.php b/test/unit/models/classes/xml/XmlEditorTest.php
index 7f15f1535..bd00d89d9 100644
--- a/test/unit/models/classes/xml/XmlEditorTest.php
+++ b/test/unit/models/classes/xml/XmlEditorTest.php
@@ -1,9 +1,28 @@
 <?php
 
+/**
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; under version 2
+ * of the License (non-upgradable).
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ * Copyright (c) 2020-2023 (original work) Open Assessment Technologies SA.
+ */
+
 namespace oat\taoQtiTest\test\unit\models\classes\xml;
 
 use core_kernel_classes_Resource;
 use oat\generis\test\TestCase;
+use oat\tao\model\featureFlag\FeatureFlagChecker;
 use oat\taoQtiTest\models\xmlEditor\XmlEditor;
 use PHPUnit\Framework\MockObject\MockObject;
 use qtism\data\storage\xml\XmlDocument;
@@ -16,33 +35,40 @@
 
 class XmlEditorTest extends TestCase
 {
-    /**
-     * @var XmlDocument
-     */
+    /** @var XmlDocument */
     private $xmlDoc;
-    /**
-     * @var core_kernel_classes_Resource|MockObject
-     */
+
+    /** @var core_kernel_classes_Resource|MockObject */
     private $testResourceMock;
-    /**
-     * @var ServiceLocatorInterface
-     */
+
+    /** @var ServiceLocatorInterface */
     private $serviceLocatorMock;
-    /**
-     * @var MockObject|taoQtiTest_models_classes_QtiTestService
-     */
+
+    /** @var taoQtiTest_models_classes_QtiTestService|MockObject */
     private $qtiTestServiceMock;
 
+    /** @var FeatureFlagChecker|MockObject */
+    private $featureFlagCheckerMock;
+
     public function setUp(): void
     {
         $doc = new XmlDocument();
         $doc->load(__DIR__ . '/../../../../samples/xml/test.xml');
         $this->xmlDoc = $doc;
+
         $this->testResourceMock = $this->createMock(core_kernel_classes_Resource::class);
+
         $this->qtiTestServiceMock = $this->createMock(taoQtiTest_models_classes_QtiTestService::class);
-        $this->qtiTestServiceMock->method('getDoc')->with($this->testResourceMock)->willReturn($this->xmlDoc);
+        $this->qtiTestServiceMock
+            ->method('getDoc')
+            ->with($this->testResourceMock)
+            ->willReturn($this->xmlDoc);
+
+        $this->featureFlagCheckerMock = $this->createMock(FeatureFlagChecker::class);
+
         $this->serviceLocatorMock = $this->getServiceLocatorMock([
-            taoQtiTest_models_classes_QtiTestService::class => $this->qtiTestServiceMock
+            taoQtiTest_models_classes_QtiTestService::class => $this->qtiTestServiceMock,
+            FeatureFlagChecker::class => $this->featureFlagCheckerMock,
         ]);
     }
 
@@ -145,6 +171,13 @@ public function testSaveStringTest()
     public function testIsLocked()
     {
         $service = new XmlEditor([XmlEditor::OPTION_XML_EDITOR_LOCK => false]);
+        $service->setServiceLocator($this->serviceLocatorMock);
+
+        $this->featureFlagCheckerMock
+            ->method('isEnabled')
+            ->with('XML_EDITOR_ENABLED')
+            ->willReturn(true);
+
         $this->assertEquals(false, $service->isLocked());
     }
 }