Matching routes with :constraints in functional tests

There is a problem of getting routes with :constraints matched with get, post etc. in functional tests.

# config/routes.rb
TestTest::Application.routes.draw do |map|
  resources :users do
    scope :constraints => {:user_id => /[a-z0-9]+/i} do
      resource :license
    end
  end
end

# test/functional/licenses_controller_test.rb
require 'test_helper'

class LicensesControllerTest < ActionController::TestCase
  test "stuff" do
    matched_params = TestTest::Application.routes.recognize_path("/users/123abc/license")
    p matched_params
    # => {:controller=>"licenses", :user_id=>"123abc", :action=>"show"}

    begin
      TestTest::Application.routes.generate(matched_params)
    rescue => e
      p e
      # => #<ActionController::RoutingError: No route matches {:action=>"show", :user_id=>"123abc", :controller=>"licenses"}>
    end
    
    get :show, :user_id => "123abc"
    # => ActionController::RoutingError: No route matches {:controller=>"licenses", :action=>"show", :user_id=>"123abc"}
  end
end

If the :constraints are removed, the test will pass.

The routes match when running the app, so it seems like it is a functional test issue.

This also only occurs in 1.8.7 - the test above runs fine in 1.9.x.

Pushed an example Rails application you can git clone to easily replicate the issue yourself: http://github.com/augustl/Rails-3-functional-test-problem

Attached is a passing test case that also tries to replicate the issue, but that test actually passes.