I ended up publishing it in two parts :-) Here are the URLs:
http://hcoder.org/2012/02/13/unit-testing-advice-for-seasoned-hackers-12/ http://hcoder.org/2012/02/15/unit-testing-advice-for-seasoned-hackers-22/
Now I'll have a look at the coverage and see what I can do for the unit tests before I move on to Stem/chutney.