Run their code via unit tests. We've assumed if you've written a unit test for a function, the state will be taken care of.

Ah, this is similar to what Gilad Bracha is doing in his live programming work for NewSpeak.

That sounds really interesting, can you share any articles or videos about his work on live programming?

It was some things he demonstrated at WGLD meetings; here is a blog post with the same title as his talk:

http://gbracha.blogspot.com/2012/11/debug-mode-is-only-mode....

And later:

http://gbracha.blogspot.com/2013/04/making-methods-live.html

He is giving a keynote at ECOOP on the topic in June.

seanmcdirmid I just checked out your paper about live coding (with pacman video). Did you see http://worrydream.com/LearnableProgramming/ ? Do you guys consider collaborating?

I saw that in 2012 (I started my own research in 2007). At the time...I sent an email to Bret Victor, but he never replied (I hear he is busy).

The pacman video paper is really old (2007), you should check out my newer ones :)