Trace source of deprecation warnings in rails tests

Question

When running my functional tests, I'm getting the following warning in one of the test cases but I can't pinpoint where it's coming from:

gems/actionpack-2.3.8/lib/action_controller/record_identifier.rb:76: warning: Object#id will be deprecated; use Object#object_id

Unfortunately that's the only line of the backtrace that's shown, even if I run it with rake test --trace, and there is no more information in log/test.log.

How can I get the full backtrace for this warning or otherwise figure out which line in my code is causing it?

Answer 1

When I get this kind of warning in my tests it is usually because I am using mocking model objects and am not providing all the methods that active record provides for real.

A good starting point would be the rails code itself. Looking at the source code for the action_pack gem which is referenced, the method that is causing the error is dom_id. That method generates an id for an object for use on a page. It seems to be called in a couple of places internally (unless you are calling it directly of course!) but the most likely cause appears to be calling form_for on an object.