title: Rails / Factory Girl: Uninitialized constant FactoryGirl (NameError)
body: <p>I installed the <code>factory_girl</code> gem, and when I run my tests I get an error:</p>
  
  <blockquote>
    <p>`block in ': uninitialized constant FactoryGirl (NameError)</p>
  </blockquote>
  
  <p>This is my <code>spec_helper.rb</code></p>
  
  <pre class="lang-ruby prettyprint-override"><code>RSpec.configure do |config|
    config.include FactoryGirl::Syntax::Methods
    config.expect_with :rspec do |expectations|
      expectations.include_chain_clauses_in_custom_matcher_descriptions = true
    end
    config.mock_with :rspec do |mocks|
      mocks.verify_partial_doubles = true
    end
  end
  </code></pre>
  
  <p>How can it be fixed?</p>