sqlalchemy inheritance test case

test.py

from sqlalchemy import Column, Integer
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()


class C(Base):
    __tablename__ = 'C'

    id = Column(Integer, primary_key=True)
    t = Column(Integer)

    __mapper_args__ = {
        'polymorphic_on': t,
        'polymorphic_identity': 1,
    }

assert C().t == 1

class D(C):
    __mapper_args__ = {
        'polymorphic_identity': 2,
    }

assert D().t == 2

class D2(D):
    foo = 'bar'

assert D2().t == 2