testing: No route matches {:action=>"show", :controller=>"users", :id=>nil}
===

I only have 2 weeks learning ruby and ruby on rails. 
currently my problem is with te routes matches I don't understand so much, now I'm testing with rspec this:

    require 'spec_helper'

    describe UsersController do

	it "should redirect to the user show page" do
    post :create, :users => @attr
    response.should redirect_to(user_path(assigns(:users)))
    end
      describe "signup" do

    before { visit new_user_registration_path }

    let(:submit) { "Sign up" }

    describe "with invalid information" do
      it "should not create a user" do
        expect { click_button submit }.not_to change(User, :count)
      end
    end

    describe "with valid information" do
      before do
        fill_in "Email", :with=> "user@example.com"
        fill_in "Password", :with=> "foobar"
        #fill_in "password_confirmation", :with=> "foobar"
      end

      it "should create a user" do
        expect { click_button submit }.to change(User, :count).by(1)
      end
    end
    end
    end 

i have this on my UserController

    class UsersController < ApplicationController

	def new
		 @user = User.new
  	end
 
  	def create
  		@user = User.new(params[:user])
		if @user.save
   			redirect_to user_session_path
		else
 		redirect_to new_user_session_path
	end

	end

	def show
  		@user = User.find(params[:id])
  		#redirect_to @user
	end
    end

but when I run the test i got this error:

    Failures:

    1) UsersController should redirect to the user show page
       Failure/Error: response.should redirect_to(user_path(assigns(:users)))
       ActionController::RoutingError:
       No route matches {:action=>"show", :controller=>"users", :id=>nil}
       # ./spec/controllers/user_controller_spec.rb:7

    2) UsersController signup with valid information should create a user
       Failure/Error: expect { click_button submit }.to change(User, :count).by(1)
       count should have been changed by 1, but was changed by 0
       # ./spec/controllers/user_controller_spec.rb:29