As for the 'freezing', I've been thinking about it in other contexts as well. I noticed that one of the companies I worked at seemed to want to do some of their regression tests that way, so it makes sense to provide a way to automate it.
In particular, I would like a way to convert an interactive console session (my normal method of testing code) into a set of unit tests. Not sure exactly what the right way to do that would be though.
It's still not a very good form of unit test, as it won't cover cases as mentioned above with randomness or side-effects. Mutation testing or fuzz testing / generators are probably better ways to generate unit tests, but they don't make very good examples.