Ruby on Rails

I'm copying this directly from Stack Overflow to see if anyone can help. Here is the link to my question on Stack Overflow:

http://stackoverflow.com/questions/18006056/rspec-error-undefined-method-downcase-for-nilnilclass

I keep getting this error when running my Rspec test and can't figure out why. I'm pretty new to Rails (and programming in general) so any direction or help would be much appreciated!

Failures:    1) User pages profile page    Failure/Error: before { visit user_path(user) }   ActionView::Template::Error:     undefined method `downcase' for nil:NilClass   # ./app/helpers/users_helper.rb:5:in `gravatar_for'   # ./app/views/users/show.html.erb:3:in `_app_views_users_show_html_erb__1766857043046396980_38603940'   # ./spec/requests/user_pages_spec.rb:9:in `block (3 levels) in <top (required)>'    2) User pages profile page    Failure/Error: before { visit user_path(user) }   ActionView::Template::Error:     undefined method `downcase' for nil:NilClass   # ./app/helpers/users_helper.rb:5:in `gravatar_for'   # ./app/views/users/show.html.erb:3:in `_app_views_users_show_html_erb__1766857043046396980_38603940'   # ./spec/requests/user_pages_spec.rb:9:in `block (3 levels) in <top (required)>'    Finished in 0.46129 seconds  39 examples, 2 failures    Failed examples:    rspec ./spec/requests/user_pages_spec.rb:12 # User pages profile page   rspec ./spec/requests/user_pages_spec.rb:11 # User pages profile page 

I'm in Chapter 7.13 of the Ruby on Rails tutorial. The tests cleared just fine until I added the Gravatar code and FactoryGirls Gem.

/app/helpers/users_helper.rb file

module UsersHelper      # Returns the Gravatar (http://gravatar.com/) for the given user.    def gravatar_for(user)      gravatar_id = Digest::MD5::hexdigest(user.email.downcase)      gravatar_url = "https://secure.gravatar.com/avatar/#{gravatar_id}"      image_tag(gravatar_url, alt: user.name, class: "gravatar")    end  end

spec/requests/user_pages_spec.rb

require 'spec_helper'    describe "User pages" do      subject { page }      describe "profile page" do      let(:user) { FactoryGirl.create(:user) }      before { visit user_path(user) }        it { should have_content(user.name) }      it { should have_title(user.name) }    end  .  .  .  end

And the last reference: app/views/users/show.html.erb

<% provide(:title, @user.name) %>  <h1>    <%= gravatar_for @user %>    <%= @user.name %>   </h1>

Here is the factory file:

FactoryGirl.define do    factory :user do      name     "Michael Hartl"      email    "michael@example.com"      password "foobar"      password_confirmation "foobar"    end  end