'Test that FileField.save_form_data, if passed a truthy value, updates
its instance attribute.'

def test_changed(self):

    d = Document(myfile=u'something.txt')
    self.assertEqual(d.myfile, u'something.txt')
    field = d._meta.get_field(u'myfile')
    field.save_form_data(d, u'else.txt')
    self.assertEqual(d.myfile, u'else.txt')
