sqlalchemy + pytest patch session to avoid commits on tests

conftest.py

import pytest

@pytest.yield_fixture(scope='session')
def patch_session():
    def commit():
        """Flush and expire caches."""
        db.session.flush()
        db.session.expire_all()

    old_commit = db.session.commit
    db.session.commit = commit
    yield
    db.session.commit = old_commit