How to use Factory Boy with SQLAlchemy session (Lazy Loaded) correctly?

I just run into a problem with my testsuite. I am using a setup with nosetests, SQLAlchemy, Flask and Factory-Boy

I have the following code:

def _create_fixtures(self):
    self.user = UserFactory()
    pprint(db.query(User).all())
    db.add(self.user)
    pprint(db.query(User).all())

witch returns following:

[<User #1>, <User #2>]
[<User #1>, <User #2>]

My UserFactory looks like this:

class UserFactory(Factory):
    FACTORY_FOR = User
    FACTORY_SESSION = db
    email = Sequence(lambda n: 'user{0}@wohnortfinder.com'.format(n))
    password = "password"
    username = Sequence(lambda n: 'user{0}'.format(n))

(yes I am using the normal Factory and not he SQLAlchemy factory, cause this didn't work either)

Why isn't my Factory Object stored to db? It doesn't raise an error, it just doesn't save. I mean even when the current transaction is not committed yet, the query later should queries the actual transaction, shouldn't it?

Oddly when I manually commit the session, it raises an error.

InvalidRequestError: No transaction is begun.

Even though I began a transaction when creating the session object.

def init_engine(uri, **kwargs):
    global engine
    engine = create_engine(uri, **kwargs)
    Base.metadata.create_all(engine)
    db.begin()
    return engine


engine = None

db = scoped_session(lambda: create_session(bind=engine))

any idea why this is not working?

Thanks for your thoughts

Solution

You can define the factory_boy factories without setting the SQLAlchemy session and then set it up in between initialising the Flask app and using the factories by assigning to the _meta property of the factory class:

db_session = set_up_a_db_session_somehow()
MyFactoryClass._meta.sqlalchemy_session = db_session

This seems to work fine with a scoped session.