how can I run rails at a URI containing a folder path?

I'd like to serve a particular rails app at <my ip address>/test and
my webserver is serving up the app when I visit that URI but as
suspected, rails looks for a controller or method called "test" and I
get the following error message:
No route matches "/test" with {:method=>:get}

Can someone tell me what config change I need to make? I thought it
might be the following line in config/environment.rb but I can't get
it to work by editing it.
config.load_paths += %W( {RAILS_ROOT}/extras )

Sounds like you're looking for relative_url_root:

Thank you