diff --git a/tests/NestedSetsBehaviorTest.php b/tests/NestedSetsBehaviorTest.php
index e00b854..7e90ee9 100644
--- a/tests/NestedSetsBehaviorTest.php
+++ b/tests/NestedSetsBehaviorTest.php
@@ -10,7 +10,7 @@
 use yii\db\{ActiveRecord, Exception, StaleObjectException};
 use yii\helpers\ArrayHelper;
 use yii2\extensions\nestedsets\NestedSetsBehavior;
-use yii2\extensions\nestedsets\tests\support\model\{MultipleTree, Tree};
+use yii2\extensions\nestedsets\tests\support\model\{MultipleTree, Tree, TreeWithStrictValidation};
 
 use function get_class;
 use function sprintf;
@@ -1782,4 +1782,52 @@ public function testThrowExceptionWhenAppendToParentWithNullRightValue(): void
 
         $childNode->appendTo($parentNode);
     }
+
+    public function testAppendToWithRunValidationParameterUsingStrictValidation(): void
+    {
+        $this->generateFixtureTree();
+
+        $targetNode = Tree::findOne(2);
+
+        self::assertNotNull(
+            $targetNode,
+            'Target node with ID \'2\' should exist before calling \'appendTo\'.',
+        );
+
+        $invalidNode = new TreeWithStrictValidation(['name' => 'x']);
+
+        $result1 = $invalidNode->appendTo($targetNode);
+        $hasError1 = $invalidNode->hasErrors();
+
+        self::assertFalse(
+            $result1,
+            '\'appendTo()\' should return \'false\' when \'runValidation=true\' and data fails validation.',
+        );
+        self::assertTrue(
+            $hasError1,
+            'Node should have validation errors when \'runValidation=true\' and data is invalid.',
+        );
+
+        $invalidNode2 = new TreeWithStrictValidation(['name' => 'x']);
+
+        $result2 = $invalidNode2->appendTo($targetNode, false);
+        $hasError2 = $invalidNode2->hasErrors();
+
+        self::assertTrue(
+            $result2,
+            '\'appendTo()\' should return \'true\' when \'runValidation=false\', even with invalid data ' .
+            'that would fail validation.',
+        );
+        self::assertFalse(
+            $hasError2,
+            'Node should not have validation errors when \'runValidation=false\' because validation was skipped.',
+        );
+
+        $persistedNode = TreeWithStrictValidation::findOne($invalidNode2->id);
+
+        self::assertNotNull(
+            $persistedNode,
+            'Node should exist in database after appending to target node with validation disabled.',
+        );
+    }
 }
diff --git a/tests/phpstan-config.php b/tests/phpstan-config.php
index 80f2b65..d25d0c1 100644
--- a/tests/phpstan-config.php
+++ b/tests/phpstan-config.php
@@ -4,7 +4,13 @@
 
 use yii\db\{ActiveQuery, ActiveRecord};
 use yii2\extensions\nestedsets\{NestedSetsBehavior, NestedSetsQueryBehavior};
-use yii2\extensions\nestedsets\tests\support\model\{MultipleTree, MultipleTreeQuery, Tree, TreeQuery};
+use yii2\extensions\nestedsets\tests\support\model\{
+    MultipleTree,
+    MultipleTreeQuery,
+    Tree,
+    TreeQuery,
+    TreeWithStrictValidation,
+};
 
 return [
     'behaviors' => [
@@ -26,5 +32,8 @@
         TreeQuery::class => [
             NestedSetsQueryBehavior::class,
         ],
+        TreeWithStrictValidation::class => [
+            NestedSetsBehavior::class,
+        ],
     ],
 ];
diff --git a/tests/support/model/TreeWithStrictValidation.php b/tests/support/model/TreeWithStrictValidation.php
new file mode 100644
index 0000000..8f61831
--- /dev/null
+++ b/tests/support/model/TreeWithStrictValidation.php
@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace yii2\extensions\nestedsets\tests\support\model;
+
+/**
+ * @property int $id
+ * @property int $lft
+ * @property int $rgt
+ * @property int $depth
+ * @property string $name
+ */
+final class TreeWithStrictValidation extends Tree
+{
+    public function rules(): array
+    {
+        return [
+            ['name', 'required', 'message' => 'Name cannot be blank.'],
+            ['name', 'string', 'min' => 5, 'message' => 'Name must be at least 5 characters long.'],
+            ['name', 'match', 'pattern' => '/^[A-Z]/', 'message' => 'Name must start with an uppercase letter.'],
+        ];
+    }
+}