title: Capybara with :js => true causes test to fail
body: <p>I'm new to Capybara and testing on Rails in general, so please forgive me if this is a simple answer.</p>
  
  <p>I've got this test</p>
  
  <pre><code>it "should be able to edit an assignment" do
      visit dashboard_path
      select(@project.client + " - " + @project.name, :from =&gt; "assignment_project_id")
      select(@team_member.first_name + " " + @team_member.last_name, :from =&gt; "assignment_person_id")
      click_button "Create assignment"
      page.should have_content(@team_member.first_name)
  end
  </code></pre>
  
  <p>it passes as is, but if I add :js => true it fails with</p>
  
  <pre><code>cannot select option, no option with text 'Test client - Test project' in select box 'assignment_project_id'
  </code></pre>
  
  <p>I'm using FactoryGirl to create the data, and as the test passes without JS, I know that part is working. </p>
  
  <p>I've tried with the default JS driver, and with the :webkit driver (with capybara-webkit installed)</p>
  
  <p>I guess I don't understand enough what turning on JS for Capybara is doing.</p>
  
  <p>Why would the test fail with JS on?</p>