py.test + SQLAlchemy transactional testing

conftest.py

import pytest
from turbogears.database import get_engine, session


@pytest.fixture(autouse=True)
def wrap_transaction(request):
    """Automatically wrap test cases in a transaction, rolled back on
    completion. Uses an "external," non-ORM transaction that is durable
    against inner transactions used by the ORM. Thanks to @sontek

        http://sontek.net/blog/detail/writing-tests-for-pyramid-and-sqlalchemy

    """

    connection = get_engine().connect()

    # begin a non-ORM transaction
    transaction = connection.begin()
    session.bind = connection

    def _tear_down():
        transaction.rollback()
        session.close()
        connection.close()

    request.addfinalizer(_tear_down)