title: uninitialized constant Test::Unit::UI::XML (NameError) in Rails (or Ruby)
body: <p>I'm trying to create an xml runner to make a result report of Rails unit testing. Here is a code I have:</p>
  
  <pre><code>require 'test/unit'
  require 'test/unit/ui/console/testrunner'
  
  class FastFailRunner &lt; Test::Unit::UI::Console::TestRunner
    def add_fault(fault)
      @faults &lt;&lt; fault
      nl
      output("%3d) %s" % [@faults.length, fault.long_display])
      output("--")
      @already_outputted = true
    end
  
    def finished(elapsed_time)
      nl
      output("Finished in #{elapsed_time} seconds.")
      nl
      output(@result)
    end
  end
  
  Test::Unit::AutoRunner::RUNNERS[:fastfail] = proc do |r|
    FastFailRunner
  end
  </code></pre>
  
  <p>When I run it as <code>TESTOPTS="/home/alex/RubymineProjects/app2/test/unit/runner.rb --runner=xml" rake test</code> </p>
  
  <p>... I get an error (pretty weird error)</p>
  
  <pre><code>/home/alex/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/ext/module.rb:36:in `const_missing': uninitialized constant Test::Unit::UI::XML (NameError)
      from /home/alex/.rvm/gems/ruby-1.9.3-p194/gems/test-unit-2.5.2/lib/test/unit/runner/xml.rb:5:in `block in &lt;module:Unit&gt;'
      from /home/alex/.rvm/gems/ruby-1.9.3-p194/gems/test-unit-2.5.2/lib/test/unit/autorunner.rb:389:in `[]'
      from /home/alex/.rvm/gems/ruby-1.9.3-p194/gems/test-unit-2.5.2/lib/test/unit/autorunner.rb:389:in `run'
      from /home/alex/.rvm/gems/ruby-1.9.3-p194/gems/test-unit-2.5.2/lib/test/unit/autorunner.rb:58:in `run'
      from /home/alex/.rvm/gems/ruby-1.9.3-p194/gems/test-unit-2.5.2/lib/test/unit.rb:501:in `block in &lt;top (required)&gt;'
  gem install minitest
  /home/alex/.rvm/gems/ruby-1.9.3-p194/gems/test-unit-2.5.2/lib/test/unit/runner/xml.rb:5:in `block in &lt;module:Unit&gt;': uninitialized constant Test::Unit::UI::XML (NameError)
      from /home/alex/.rvm/gems/ruby-1.9.3-p194/gems/test-unit-2.5.2/lib/test/unit/autorunner.rb:389:in `[]'
      from /home/alex/.rvm/gems/ruby-1.9.3-p194/gems/test-unit-2.5.2/lib/test/unit/autorunner.rb:389:in `run'
      from /home/alex/.rvm/gems/ruby-1.9.3-p194/gems/test-unit-2.5.2/lib/test/unit/autorunner.rb:58:in `run'
      from /home/alex/.rvm/gems/ruby-1.9.3-p194/gems/test-unit-2.5.2/lib/test/unit.rb:501:in `block in &lt;top (required)&gt;'
  Errors running test:units! #&lt;RuntimeError: Command failed with status (1): [/home/alex/.rvm/rubies/ruby-1.9.3-p194/bin...]&gt;
  Errors running test:functionals! #&lt;RuntimeError: Command failed with status (1): [/home/alex/.rvm/rubies/ruby-1.9.3-p194/bin...]&gt;
  </code></pre>
  
  <p>I tried to require <code>test/unit/ui/xml/testrunner.rb</code> but no luck.
  Any thoughts?</p>