CakePHP authentication return false - cakephp

Question

I have an error with CakePHP, the authentication method always returns false in development environment but works fine in production environment.
When debugging $this->data in my UsersController, the password is not visible. Is this normal operation?
What is the correct way to debug this method ?
$this->data :
array(
'User' => array(
'password' => '*****',
'username' => 'martin'
)
)
My login function in UsersController.
public function login() {
if($this->request->is('post')){
if($this->Auth->login()){
// Mise à jour nombre de connexion
$this->User->updateAll(array(
'User.nb_cnx' => 'User.nb_cnx + 1'
), array(
'User.id' => $this->Auth->user('id')
));
// Mise à jour dernière date de connexion
$this->User->id = $this->Auth->user('id');
$this->User->saveField('last_cnx', date('Y-m-d H:i:s'));
// Petit nettoyage au cas où
$this->Session->delete('Article');
$this->Session->delete('Stock');
$this->Session->delete('Commande');
$this->Session->delete('RetourAdmin');
if($this->Cookie->read('Commande')){
$this->Session->write('Commande', $this->Cookie->read('Commande'));
}
return $this->redirect($this->Auth->redirectUrl());
}else{
$this->Flash->error(__('Votre nom d\'user ou mot de passe sont incorrects.'));
}
}
if($this->Session->read('Auth.User')){
$this->Session->setFlash('Vous êtes connecté!');
return $this->redirect('/');
}
}