import unittest from email import policy from test.test_email import TestEmailBase class Test(TestEmailBase): policy = policy.default def test_error_on_setitem_if_max_count_exceeded(self): m = self._str_msg("") m['To'] = 'abc@xyz' with self.assertRaises(ValueError): m['To'] = 'xyz@abc' if __name__ == '__main__': unittest.main()