There is one chapter (chapter 7) which covers mock objects. It's even printable from somewhere, since I have a printout on my desk. It's a very interesting read. In that chapter, he mentions that he will cover more about mock objects elsewhere in the book.
I imangine the first chapter should explain what unit testing is and why
you should do it. Of course, if you can find one instance where it took a couple of programmers a few hours to find a minor bug which a unit test would have shown immediately, or if you can show a regression that occured which could have been avoided with unit tests in place, you pretty much make the case for unit testing.
L