In python, is there a good idiom for using context managers in setup/teardown

How about overriding unittest.TestCase.run() as illustrated below? This approach doesn’t require calling any private methods or doing something to every method, which is what the questioner wanted.

from contextlib import contextmanager
import unittest

@contextmanager
def resource_manager():
    yield 'foo'

class MyTest(unittest.TestCase):

    def run(self, result=None):
        with resource_manager() as resource:
            self.resource = resource
            super(MyTest, self).run(result)

    def test(self):
        self.assertEqual('foo', self.resource)

unittest.main()

This approach also allows passing the TestCase instance to the context manager, if you want to modify the TestCase instance there.