def truncate_db(engine):
    # delete all table data (but keep tables)
    # we do cleanup before test 'cause if previous test errored,
    # DB can contain dust
    meta = MetaData(bind=engine, reflect=True)
    con = engine.connect()
    trans = con.begin()
    con.execute('SET FOREIGN_KEY_CHECKS = 0;')
    for table in meta.sorted_tables:
        con.execute(table.delete())
    con.execute('SET FOREIGN_KEY_CHECKS = 1;')
    trans.commit()