Replacing a method without passthrough.

After being introduced to Mocker by Mike at a recent Portland Python meeting, I'm trying it out with this integration test I'm writing. There's one part left I'm not quite sure how to do, which looks something like this:

class Message(object):
    def send(self, destination):
        # Does network stuff I don't want the tests to invoke.
        socket.blahblahblah

class OurClass(object):

    messageClass = Message

    def __init__(self, where):
        self.there = where

    def yell(self):
        m = self.messageClass()
        m.send(self.there)

class TestWithoutMocker(TestCase):

    def test_yell(self):
        send_list = []
        class FakeMessage(Message):
            def send(self, destination):
                # Don't passthrough! That would be bad.
                send_list.append(destination)

        that = OurClass("there")
        that.messageClass = FakeMessage
        that.yell()
        self.failUnlessEqual(["there"], send_list)

# end

I tried to figure out how to use mocker to provide an expectation and result for Message.send without passthrough, but I haven't quite got it yet.