def METHOD_NAME(sub_type):
    """
    Run background test separately with main_test.
    background test: e.g. rng_bat/balloon_test/netperf ...
    main test: e.g. reboot/shutdown/stop/cont/driver_load ...
    :params: sub_type: Background test.
    """
    if params.get("bg_stress_test_is_cmd", "no") == "yes":
        session = vm.wait_for_login()
        sub_type = utils_misc.set_winutils_letter(
            session, sub_type)
        session.cmd(sub_type, timeout=600)
        session.close()
    else:
        utils_test.run_virt_sub_test(test, params, env, sub_type)