Form Error Messages Are Not Displayed Laravel 5

I'm new at Laravel and I want to Use the authentification system included in Laravel. To do so I activated authentification in my laravel projet with

php artisant make:auth

Then I tryed to log in in the my projet and everthing works but the error messages like "e-mail field is required" aren't shown when I submit the empty form.

Here is an example of the error test auto implemented in my login.blade.php :

<div class="form-group">
          <div class="col-md-12">
              <input id="email" type="email" class="form-control" placeholder="" name="email" value="" required autofocus>

              @if ($errors->has('email'))
                  <span class="help-block">
                      <strong></strong>
                  </span>
              @endif
          </div>
</div>

Please notice that when I enter a bad combinaison of email/password the error message is shown correctly but for any other case the page doesn't even refresh.

Thank you for your help ...

via Chebli Mohamed