I've been retrofitting test suites onto applications in my archives. This is not really an automated method, but I feed can_ok() methods using foreach iterating across an array of methods gleaned with:

grep ^sub Module.pm | sed "s/^sub //" | sed "s/{.*$//"
[download]

But as already mentioned in this thread, this does nothing to discern between public and private methods, though were you to adopt the convention of naming private methods with a leading underbar, or if you managed to actually document with pod, EVERY public method, then your string manipulations could be massaged to dissect perldoc instead, and get an accurate list.

-- Hugh