def METHOD_NAME(self, now, db, default_namespace):
    shard_id = default_namespace.id >> 48
    query = "SELECT count(id) FROM transaction WHERE namespace_id={}".format(
        default_namespace.id
    )
    all_transactions = db.session.execute(query).scalar()
    # Ensure no transactions are deleted during a dry run
    purge_transactions(shard_id, days_ago=30, dry_run=True, now=now)
    assert db.session.execute(query).scalar() == all_transactions