Extract paths to helper methods

app/helpers/application_helper.rb

@@ -1,2 +1,9 @@
 module ApplicationHelper
+  def twitter_auth_path
+    "/auth/twitter"
+  end
+
+  def github_auth_path
+    "/auth/github"
+  end
 end

app/views/layouts/application.html.erb

@@ -18,8 +18,8 @@
           <% if current_user %>
             <li><%= link_to "Sign out", logout_path %></li>
           <% else %>
-            <li><%= link_to "Twitter Sign in", "/auth/twitter" %></li>
-            <li><%= link_to "Github Sign in", "/auth/twitter" %></li>
+            <li><%= link_to "Twitter Sign in", twitter_auth_path %></li>
+            <li><%= link_to "Github Sign in", github_auth_path %></li>
           <% end %>
         </ul>
       </div>