This is an example CWEB program I did back in 2002. It is a moderately interesting literate programming example.
I happened to futz with this on OS X, and you're going to need some amount of CWEB tools, most notably ctangle and cweave. I also happen to like making PDFs myself (instead of DVIs), so I use pdftex (instead of tex) too.
By default, it makes a program called sha256 which will run some unit tests.