class SomeTest(ORMTest):

    def define_tables(self, metadata):
        self.users = Table('users', metadata, ...)
        self.addresses = Table('addresses', metadata, ...)

    def define_classes(self):
        class User(object):
            pass
        class Address(object):
            pass

        self.User = User
        self.Address = Address

    def test_1(self):
        mapper(self.User, self.users)
        # ...

    def test_2(self):
        mapper(self.Address, self.addresses, properties={
                'user': relation(self.User)
                })
        # ...