So something like...

    var button = this.button,
        expected = button.getNode().getHTML(),
        actual = button.get('labelHTML');

Which essentially points to the same DOM method, one is just passed through ButtonCore before the test gets the result?

I guess that makes sense though considering this unit test isn't to ensure the DOM's behavior is correct, but rather that ButtonCore does the right thing with what the DOM (and `Y.Node`) gives it.