title: Backtrace Silencer not working
body: <p>In my Rails app, I have set up the following backtrace silencer, as suggested by Michael Hartl in his Rails tutorial:</p>
  
  <pre><code>Rails.backtrace_cleaner.add_silencer { |line| line =~ /rvm/ }
  </code></pre>
  
  <p>But still I get all the noise I intended to filter out:</p>
  
  <pre><code>7:13:55 - INFO - Running: test/controllers/tags_controller_test.rb
  Started
  
  ERROR["test_should_get_index", TagsControllerTest, 0.45206]
  test_should_get_index#TagsControllerTest (0.45s)
  ActionController::UrlGenerationError:               
  ActionController::UrlGenerationError: No route matches {:action=&gt;"index", :controller=&gt;"tags"}
          /Users/chris/.rvm/gems/ruby-2.0.0-p353/gems/actionpack-4.1.6/lib/action_dispatch/journey/formatter.rb:39:in `generate'
          /Users/chris/.rvm/gems/ruby-2.0.0-p353/gems/actionpack-4.1.6/lib/action_dispatch/routing/route_set.rb:599:in `generate'
  </code></pre>
  
  <p>Clearly the string "rvm" is present in the last two lines. But still they show up. Changing the string to ".rvm" didn't make any difference.</p>