Rspec error: undefined method 'change' for end.should change(Model, :count)

This is a follow on after completing the Ruby on Rails tutorial.

I've spent quite a while trying to mix and match gems to find a solution since I really have no idea how Rspec is having trouble identifying 'change'.

Error: /spec/requests/athletes_spec.rb:20:inblock (3 levels) in ': undefined method change' for #<Class:0x00000100e715e8> (NoMethodError)

require 'spec_helper'

describe "Athletes" do

  before(:each) do
    @attr = { :gender => "male",
        :age => 20,
      :height => 120,
      :weight => 100,
      :skill => 2
    }
    @user = Factory(:user)
  end

  describe "Creating Athletes" do

    describe "with the correct user should work" do
      lambda do
        post :create, :athlete => @attr
      end.should_not change(Athlete, :count)

    end

  end
end

I love the concept of TDD but it seem开发者_JAVA百科s like half the time I'm trying to get the testing environment to work. Can anyone tell me where I'm going wrong?

FURTHER EDIT:

Here's my Gemfile:

source 'http://rubygems.org'

gem 'rails', '3.0.4'
gem 'sqlite3-ruby', '1.3.2', :require => 'sqlite3'
gem "will_paginate", "3.0.pre2"
gem 'jquery-rails', '>= 0.2.6'



group :development do
  gem 'rspec-rails', '2.5.0'
  gem 'annotate-models'
end

group :test do
  gem 'factory_girl_rails'
  gem 'rspec', '2.5.0'
  gem 'webrat'
end

---

First, you need to supply an example using the it keyword. Change the inner describe to it:

describe "Creating Athletes" do
  it "with the correct user should work" do

Second, in a request spec you need to specify the URI instead of the controller action, so it should read something like this (depending on your routes):

post '/athletes', :athlete => @attr

---

You could try changing:

should_not change(Athlete, :count)

to:

should_not change { Athlete.count }