Rails 2.1.0 and tzinfo plugin

I am upgrading a Rails 1.2.6 app to Rails 2.1.0 that had used tzinfo gem
to manage time zones. Time zone support is built into Rails 2.1.0 and
is based on the tzinfo gem. However, it is slightly different (I do not
know how slightly) and causes a time based test to fail that passes in
Rails 2.0.2 (since it did not have Time Zone support, it uses the tzinfo
gem and the test works).

If there is an easy way around this problem then that would be
excellent. In lieu of that, is there a way that I can coax rails to
load the tzinfo gem (freeze it into the vendor directory?) ahead of its
built-in timezone support? I might just go with it to production until
I figure out an upgrade plan.

Thanks in advance for your time.