To open the linked error file on a line number, requires the TW bin tool 'edit'.
man edit in Terminal shows the options, I used '--separate-windows' as it seems to work best for me.

In conjunction with changing the default editor in testup 'Preferences' to '/Applications/TextWrangler.app'

I edited 'editor.rb' to use TW as shown...

  def self.open_file(file, line = 0)
    editor = self.application
    if editor =~ /TextWrangler/
      command = %[edit --separate-windows "#{file}:#{line}"]
    else
      arguments = self.arguments
      arguments.gsub!('{FILE}', file)
      arguments.gsub!('{LINE}', line)
      command = %["#{editor}" #{arguments}]
    end
    system(command)
  end

for some reason #{arguments} failed to expand so I used "#{file}:#{line}".

john