Fatal error: Uncaught Error: Class 'yii\db\ActiveRecord' not found in /home/mpolsk5/public_html/visibilityfuel.com/vendor/creocoder/yii2-nested-sets/tests/models/Tree.php:21 Stack trace: #0 {main} thrown in /home/mpolsk5/public_html/visibilityfuel.com/vendor/creocoder/yii2-nested-sets/tests/models/Tree.php on line 21