Add this to your test_helper.rb to detect HTML escaping issues

assert_valid_markup.rb

  # add gem 'tidy' to your Gem file 
  # drop this snippet in class ActiveSupport::TestCase in test_helper.rb
  # then just put "assert_valid_markup" in various places in your tests
  # HTML tidy needs to be installed on your system (Snow Leopard has it installed by default)

  def assert_valid_markup(markup=@response.body)
    errors = []
    Tidy.path='/usr/lib/libtidy.dylib'   #  This is were it lives by default on OS X
    Tidy.open(:input_xml => true) do |tidy|
      tidy.options.char_encoding = 'utf8'
      tidy.clean(markup)
      errors.concat(tidy.errors)
    end
    errors << "Double escaped HTML in text (&#{$1};)" if markup =~ /&amp;(raquo|lt|gt|nbsp|amp|ldquo|rdquo)/
    errors << "Escaped HTML in text <#{$1}>" if markup =~ /&lt;([a-z]+)/
    errors << "Unescaped ampersand in text" if markup =~ /& /
    unless errors.empty?
      error_str = ''
      errors.each do |e|
        error_str += e.gsub(/\n/, "\n  ")
      end
      error_str = "XHTML Validation Failed:\n  #{error_str}"   
      assert_block(error_str) { false }
    end    
  end