test/rails_app/app/views/layouts/application.html.erb

<!DOCTYPE html>
<html>
<head>
  <title>RailsApp</title>
  <%= stylesheet_link_tag :all %>
  <%= javascript_include_tag :defaults %>
  <%= csrf_meta_tag %>
</head>
<body>
  <%= content_tag :p, flash[:notice], id: 'notice' unless flash[:notice].blank? %>
  <%= content_tag :p, flash[:alert], id: 'alert' unless flash[:alert].blank? %>

  <%= yield %>
</body>
</html>