How to test max_length option of attribute in django with SQLite?

I have a model named Article like this:

class Article(models.Model):
    title = models.CharField(max_length=50)
    content = models.TextField()
    note = models.TextField(blank=True)

when I test it use the following code:

# create the article                                                                                                          
        article = Article()
        # set the attributes                                                                                                          
        article.title = 'x'*60
        article.content = 'Good Morning, Sir'
        article.note = ''
        # save it                                                                                                                     
        article.save()

The length of title is bigger than max_length=50, but the test passed.Why?