title: Rspec - undefined method 'let'
body: <p>This is my rspec file:</p>
  
  <pre><code>require 'spec_helper'
  
  describe "Birds" do
    before { visit birds_path }
    it "should have the right title" do
      expect(page).to have_content("Approved Birds")
    end
    it "should contain the bird's name, genus, species" do
      let(:bird) { FactoryGirl.create(:bird) }
      expect(page).to have_content("#{bird.name}")
      expect(page).to have_content("#{bird.genus}")
      expect(page).to have_content("#{bird.species}")
    end
  end
  </code></pre>
  
  <p>When I run it, I get the following error:</p>
  
  <pre><code>Failure/Error: let(:bird) { FactoryGirl.create(:bird) }
   NoMethodError:
     undefined method `let' for #&lt;RSpec::Core::ExampleGroup::Nested_1:0xad87f84&gt;
  </code></pre>
  
  <p>My Gemfile has both 'rspec-rails' and 'capybara' gems. Anyone have any idea on how to fix this? 
  Thanks</p>