Why is my custom validation not being called?

I have this model and modelform:

class Comment(models.Model):
  text = models.CharField(max_length=100)

  def clean_text(self):
    print "called Comment"
    if len(self.text) <= 5:
      raise ValidationError("must have 5 chars at least")

class CommentForm(ModelForm):
  class Meta:
    model = Comment

  def clean_text(self):
    print "called CommentForm"
    if len(self.text) <= 5:
      raise ValidationError("must have 5 chars at least")

And I'm using them like this in the view:

  CommentFormSet = modelformset_factory(model=Comment,form=CommentForm,extra=3)
  if request.method == "POST":
    formset = CommentFormSet(request.POST)
    if formset.is_valid():
      print "VALID FORM"
  else:
    formset = CommentFormSet()
  return render_to_response("first.html",{开发者_开发知识库"formset":formset},context_instance=RequestContext(request))

And this is my template:

<form action="first" method="post">
  {% csrf_token %}
  {% for dict in formset.errors %}
      {% for error in dict.values %}
          {{ error }}
      {% endfor %}
  {% endfor %}
  <table>
    {{ formset }}
  </table>
  <input type="submit" value="Create"/>
</form>

The thing is, my validation is never called. I have 3 comments which I can add at once, and if their text field is empty, django says it's no problem. What am I not doing right?

EDIT: The variant with validator:

def validate_min(val):
  print "validator called"
  if len(val) <= 5:
    raise ValidationError("At least 5 characters should be provided")

class Comment(models.Model):
  text = models.CharField(max_length=100,validators=[validate_min])

My validator is not being called.

As I know models don't use clean_% methods. You should use validator.

def validate_min_length(value):
    if len(value) <= 5:
        raise ValidationError("must have 5 chars at least")

class Comment(models.Model):
    text = models.CharField(max_length=100, validators=[validate_min_length])

Edited: the answer is simple: in formset forms with no data in all fields are ignored. That's why formset is valid. Empty forms are created with empty_permitted=True. Which means they will pass validation. Override either of these and you'll get what you want.