How to configure pytest for rollback in flask-sqlalchemy 3.x

[tamarmot]

In the prior release, with SQLAlchemy 1.4 and Flask-SQLAlchemy 2.5.1, I had my conftest.py create a session for testing as follows:

connection = db.engine.connect()
 transaction = connection.begin()

 options = dict(bind=connection, binds={})
 session = db.create_scoped_session(options=options)

 db.session = session

 yield session

 transaction.rollback()
 connection.close()
 session.remove()

This would allow my pytests to use Flask-SQLAlchemy models, commit them with the session, and know that the test database was in its original state at the end of the test.

In the current 3.x release, this no longer works. I have verified that I can use SQLAlchemy directly to create a SQLAlchemy Session with sqlalchemy.orm.sessionmaker, passing it join_transaction_mode="create_savepoint". This causes begin_nested to be used, and the database is not modified at the end of my test.

I have tried passing that join_transaction_mode to the _make_scoped_session private member function, but somehow that still writes things to the database during the test, and there is no way to roll it back.

[davidism]

See #1171. Rather than trying to patch session or use private methods, patch the contents of db.engines.

[tamarmot]

Thank you! I will give it a shot.

[tamarmot]

It works beautifully! Thank you for your prompt response.