How long is a piece of string? How big's a unit?

[esther at bitranch.com]

I'm working on my monthly column for Software Test & Performance
magazine, and I'd like your input. The topic, this time around, is unit
testing (using python or anything else). Care to share some of your
hard-won knowledge with your peers?

In particular, what I'm looking for are experiences and advice about
_developing_ the unit tests. (Managing and running them is something
else again.) How big is a unit? How granular do you get? Do you have a
particular process or checklist that you follow: ensuring that your
tests look at interface, UI, etc.? Do you make a particular effort to
create unit tests for the boundary conditions?

Anecdotes are, of course, enthusiastically encouraged. Tell me what you
learned the hard way about unit testing. What mistakes have you seen
others make? What would you teach someone about the process that might
otherwise come only with experience?

On quoting you: My editors hate it when I quote "pookie-boy, whom I met
on some newsgroup." Please let me know -- privately if necessary -- how
I may refer to you in my article. (The usual format is "Kim Jones, a
programmer at BigCompany, Inc. in Denver, Colorado.")

I'll be working on this over the next several days, so I look forward
to hearing from you soon.

Esther Schindler
Contributing editor, Software Test & Performance magazine (stpmag.com)