import unittest
from unittest.mock import Mock, seal

class AsyncClass:
    async def async_method(self): pass
    def normal_method(self): pass

class Case(unittest.TestCase):
    def test_spec_normal_methods_on_class_with_mock_seal(self):
        mock = Mock(AsyncClass)
        seal(mock)
        # test passes, aka this raises AttributError
        with self.assertRaises(AttributeError):
            mock.normal_method
        # test fails, aka this does not raise AttributError
        with self.assertRaises(AttributeError):
            mock.async_method

unittest.main()