Temporarily change bgscan threshold in MultiSwitchBack

server/site_tests/network_WiFiRoaming/003SSIDMultiSwitchBack

 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This test run is designed to check that we roam successfully when signal
 # strength varies.
 { "name":"MultiSwitch",
   "steps":[
     [ "create",         { "type":"hostap" } ],
 
     [ "config",         { "channel":"2412", "mode":"11g", "pureg":None } ],
 
+    # TODO(pstew): This is a very arbitrary limit based on the testbed
+    # characteristics (expected signal and noise, as well as the range
+    # of transmit power from the AP).  We set the threshold here so that
+    # when we vary the transmit power on the AP, we will receive a
+    # "low signal" alert on the DUT.
+    [ "bgscan_set",     { "signal":"-40" }],
+
     # Connect to the first AP.
     [ "connect",        { "security":"none" } ],
     [ "client_ping",    { "count":"10" } ],
 
+    # Once the connection is up, restore the profile values to flimflam default
+    [ "bgscan_set",     { "signal":"default" }],
+
     # Create a second AP at the same time on the 5GHz radio, Channel 48
     [ "config",         { "channel":"5240", "ht40-":None, "puren":None,
                           "multi_interface":None } ],
 
     # Drop the transmit power of the first AP
     [ "set_txpower",    { "power":"fixed 0" } ],
 
     # Instead of explicitly connecting, just wait to see if the DUT
     # re-connects by itself
     [ "wait_service",   { "run_timeout":40,   # Timeout connection in 20 seconds
                           "debug":True,       # Print out all state transitions
                           "states":[
                              (None, '+ready')  # Wait for the "current AP" (as
                           ] } ],              # read off the AP)
                                               # service to transition to "ready"
     [ "client_ping",    { "count":"10" } ],
 
     # Return AP to auto transmit power
     [ "set_txpower",    { "power":"auto" } ],
 
     [ "destroy" ],
   ],
 }