I'm trying to find a way to get cts-tradefed to grab logcat files whenever there is a failure, and maybe take a bug report too. Mostly for when I'm running the full CTS plan that take so long logs at the end aren't useful
With CTS version at least 5.1_r3 you can use these options
--logcat-on-failure
--bugreport
Logs will get stored in android-cts/repository/logs/