shill: add some tips for working with autotest log files

BUG=None
TEST=None (documentation change only)

Change-Id: I250371314dd77c636fb6c4d668d46e888fab9b70
Reviewed-on: https://gerrit.chromium.org/gerrit/11283
Tested-by: mukesh agrawal <quiche@chromium.org>
Reviewed-by: Thieu Le <thieule@chromium.org>

TESTING

diff --git a/TESTING b/TESTING
index 5331229..ab647e1 100644
--- a/TESTING
+++ b/TESTING
@@ -86,6 +86,16 @@
     - rmmod mac80211_hwsim mac80211 cfg80211
     - restart wpasupplicant
     - rm /tmp/hostapd-test.control/*
+  - examine autotest log files
+    - check how far the test got before it failed
+      $ grep -a ': step ' <test output>/<suite name>/<suite name>.<test name>/debug/<suite name>.<test name>.INFO
+      e.g.
+      (chroot) $ grep -a ': step ' /tmp/run_remote_tests.abcd/network_WiFiRoaming/network_WiFiRoaming.002Suspend/debug/network_WiFiRoaming.002Suspend.INFO
+    - read the log file
+      (chroot) $ LESSOPEN= less /tmp/run_remote_tests.abcd/network_WiFiRoaming/network_WiFiRoaming.002Suspend/debug/network_WiFiRoaming.002Suspend.INFO
+
+      (LESSOPEN= prevents less from misinterpreting the logs as binary files,
+       and piping them through hexdump.)
 
 - additional test suites: we have a number of other WiFi test suites
   (in addition to WiFiManager). these are: WiFiMatFunc, WiFiPerf,