Testing private method in Ruby (rspec)

Yes, I know, that testing private methods it's not a good idea (and I read this thread - http://www.ruby-forum.com/topic/197346 - and some others)

But how can I test the following code?

I use xmpp4r. In my public method #listen I start receive jabber messages like so:

def listen
  @client.add_message_callback do |m|
    do_things_with_message(m)
  end
end

private
def do_things_with_message(m)
  #
end

#add_message_callback - runs block, when message come (in different thread)

So, testing #listen method it's difficult and it more testing xmpp4r than my #do_things_with_message

How to do all right and test #do_things_with_message?:) (http://www.ruby-forum.com/topic/197346#859664)

Refactor private methods to a new object essentialy would be as I making them a public (and class with one method - it's senselessly

EDIT: This is more a theoretical question about clean code and the correct tests. In my first link people argue that the test private methods poorly. I don't want cheat with #send, but also I don't see any viable ways to refactor

You can call a private method in ruby using the send method. Something like this:

@my_object = MyObject.new
@my_object.send(:do_things_with_message, some_message)

In a test that would look something like:

it "should do a thing" do
  my_object = MyObject.new
  my_object.send(:do_things_with_message, some_message)
  my_object.thing.should == true
end

Putting aside the question of whether or not you should be testing a private method, it is very possible in Ruby to temporarily make a private method public. Here is what I mean:

# Metaprogrammatical magic to temporarily expose
# a Class' privates (methods).
class Class
  def publicize_methods
    saved_private_instance_methods = self.private_instance_methods
    self.class_eval { public *saved_private_instance_methods }
    yield
    self.class_eval { private *saved_private_instance_methods }
  end
end

You would use publicize_methods like this:

ClassToTest.publicize_methods do
  ...
  do_private_things_with_message(m).should ???
  ...
end

You probably heard this thought in all the resources that you mention, but the proper "theoretical" way to do it would be to test that @client receives add_message_callback, and then indirectly test your private methods with integration tests. The whole point of unit testing is that you can change implementation, and your tests will still pass