Mongoid route testing problems

1. not_working

require 'spec_helper'

describe "artifact routes" do
  it "routes post /artifacts to artifacts#create" do 
    {post: "/artifacts"}.should route_to(controller: "artifacts", action: "create")
  end

  it "routes delete /artifacts/:id to artifacts#create" do 
    artifact = FactoryGirl.build(:artifact)
    {delete: "/artifacts/#{artifact._id}"}.should route_to(controller: "artifacts", action: "destroy", id: artifact._id)
  end

  it "routes put /artifacts/:id to artifacts#update" do 
    artifact = FactoryGirl.build(:artifact)
    {put: "/artifacts/#{artifact._id}"}.should route_to(controller: "artifacts", action: "update", id: artifact._id)
  end
end

2. error messages

Failure/Error: {put: "/artifacts/#{artifact._id}"}.should route_to(controller: "artifacts", action: "update", id: artifact.id)
       The recognized options <{"controller"=>"artifacts",
        "action"=>"update",
        "id"=>"51dfe0f251a6bc312a000002"}> did not match <{"controller"=>"artifacts",
        "action"=>"update",
        "id"=>"51dfe0f251a6bc312a000002"}>, difference: <{"id"=>"51dfe0f251a6bc312a000002"}>.
       <{"controller"=>"artifacts",
        "action"=>"update",
        "id"=>"51dfe0f251a6bc312a000002"}> (Hash) expected but was
       <{"controller"=>"artifacts",
        "action"=>"update",
        "id"=>"51dfe0f251a6bc312a000002"}> (ActiveSupport::HashWithIndifferentAccess).

3. working

require 'spec_helper'

describe "artifact routes" do
  it "routes post /artifacts to artifacts#create" do 
    {post: "/artifacts"}.should route_to(controller: "artifacts", action: "create")
  end

  it "routes delete /artifacts/:id to artifacts#create" do 
    artifact = FactoryGirl.build(:artifact)
    {delete: "/artifacts/#{artifact._id}"}.should route_to(controller: "artifacts", action: "destroy", id: artifact._id.to_s)
  end

  it "routes put /artifacts/:id to artifacts#update" do 
    artifact = FactoryGirl.build(:artifact)
    {put: "/artifacts/#{artifact._id}"}.should route_to(controller: "artifacts", action: "update", id: artifact._id.to_s)
  end
end