Popdog caching_extras plugin 0.1: standalone cache access and assertions

I've cleaned up and released as a plugin some code I use to both
manipulate the cache outside a request, and to test pages and
fragments have been cached/expired as expected. You can get it from:

http://svn.popdog.net/plugins/caching_extras/tags/REL-0.1/

The first feature it provides is standalone access to the fragment and
page cache. This can be useful if (like me) you have external ruby
processes that import data, and then need to expire fragments or
pages. Usage is pretty simple:

class ReportCacheManager
  include Popdog::Caching::Standalone

  def expire_salary_report
    [:xml, :xls, :html].each do |format|
      expire_page :controller => 'report', :action => 'salary',
:format => format
    end
  end
end

The other feature it provides are caching assertions, similar to those
Damien Merenne has made available in his plugin:
http://blog.cosinux.org/pages/page-cache-test

The implementation is slightly different though. Rather than mocking
out replacing the caches with temporary versions for the duration of
the assertions. It makes use of the standalone access module, so
should work within unit, functional and integration tests.

Please let me know if you have any questions/problems/ideas for
enhancement. I'm only just starting to use it in anger now, so
there's likely to be much room for improvement.

Tom