with DAV4Rack 0.2.10 in a Rails 3.2 app
dav:/webad> lock foo.txt
in lib/dav4rack/controller.rb (ligne 239), add :
response['Lock-Token'] = locktoken
and it work's but don't konw if it's valid or not.
Thanks for this report. I'm integrating the litmus test and will apply this update once I have reached the lock based tests.