class SomeTest(ORMTest):

    def define_tables(self, metadata):
        global users, addresses

        users = Table('users', metadata, ...)
        addresses = Table('addresses', metadata, ...)

    def define_classes(self):
        global User, Address

        class User(object):
            pass
        class Address(object):
            pass

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

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