import itertools
import pytest

class BaseMeta(type):
    @property
    def pytestmark(self):
        return (
            getattr(self, "_pytestmark", []) +
            list(itertools.chain.from_iterable(getattr(x, "_pytestmark", []) for x in self.__mro__))
        )

    @pytestmark.setter
    def pytestmark(self, value):
        self._pytestmark = value


class Base(object):
    # Without this metaclass, foo and bar markers override each other, and test_dings
    # will only have one marker
    # With the metaclass, test_dings will have both
    __metaclass__ = BaseMeta

@pytest.mark.foo
class Foo(Base):
    pass


@pytest.mark.bar
class Bar(Base):
    pass

class TestDings(Foo, Bar):
    def test_dings(self):
        # This test should have both markers, foo and bar.
        # In practice markers are resolved using MRO (so foo wins), unless the
        # metaclass is applied
        pass