[plt-scheme] slatex and including unit testable code

Hi folks,

I've still not looked at the details of how to use latex, but I've got
a question, and I am probably not the first one to be asking this.

I envision a scenario where I can write a tex document and in that
document include nicely formatted Scheme code. I don't want to store
the code in the tex document itself, though, because I would like to
be able to continue to modify and run said code. That way, I will
always know that my code does at least what my unit tests say it does.

How would I go about doing this?