Rspec testing conditional routing constraints

I'm trying to write some rspec integration tests to test that my conditional routes are routing correctly, but I'm getting a bunch of problems.

In routes.rb:

root :to => "error#ie6", :constraints => {:user_agent => /MSIE 6/}
root :to => "protocol_sets#index", :constraints => UserRoleConstraint.new(/doctor/i)
root :to => "refill_requests#create", :constraints => UserRoleConstraint.new(/member/i)
root :to => "refill_requests#create", :constraints => {:subdomain => "demo"}
root :to => "site#index"

In spec/requests/homepage_routing_spec.rb

require 'spec_helper'

describe "User Visits Homepage" do
  describe "Routings to homepage" do
    it "routes / to site#index when no session information exists" do
      visit root_path      
    end
  end
end

I get the following error when I try to run the test.

Failures:

  1) User Visits Homepage Routings to homepage routes / to site#index when no session information exists
     Failure/Error: visit root_path
     NoMethodError:
       undefined method `match' for nil:NilClass
     # :10:in `synchronize'
     # ./spec/requests/homepage_routings_spec.rb:6:in `block (3 levels) in '

Finished in 0.08088 seconds
1 example, 1 failure

Failed examples:

rspec ./spec/requests/homepage_routings_spec.rb:5 # User Visits Homepage Routings to homepage routes / to site#index when no session information exists

From Googling around I'm guessing there may be a problem with how rspec/capybara handle conditional routes.

Is there anyway to test constraints on routes with rspec and capybara?