If hashed password in entity, it is not get validate length of model validation

User model

PHP Code:

<?php
namespace App\Models;
use CodeIgniter\Model;
class RegisterModel extends Model
{
    protected $table = 'users';
    protected $DBGroup = 'user_webapp';
    protected $primaryKey = 'id';
    protected $allowedFields = [
        'email',
        'mobile_number',
        'password'
    ];
    protected $useTimestamps = true;
    protected $validationRules = [
        'email' => 'required|valid_email|is_unique[users.email]',
        'password'=> 'required|min_length[8]',
    ];
    protected $validationMessage = [];
    protected $returnType    = 'App\Entities\RegisterEntity';
    protected $beforeInsert = [];
} 


Entity class

PHP Code:

<?php
namespace App\Entities;
use CodeIgniter\Entity;
class RegisterEntity extends Entity
{
    public function setPassword(string $pass){
        $this->attributes['password'] = password_hash($pass, PASSWORD_BCRYPT);
        return $this;
    }
} 


Even empty password supplied, it would not trigger the validation error from model!
What is solution?