Just get a list of all pages google has indexed from your site and then use that as your basis for checking if your migration worked or not. This is very convenient because you do not have to know all your own urls yourself, and you'll only get the relevant ones (if they are not in google they are unlikely to have traffic).

The code is included as well as an example usage. He also points out FixtureShell for more command-line CakePHP examples.