Unit testing
I spent the last day and a half writing a vaguely interesting Perl module for testing some code which gives a subtly different answer each time (i.e. incorporates data from time() and /dev/urandom) and has side effects (i.e. writes to the file system). By overriding Perl's built-in 'open' function, it is possible to prefix each filename with the location of a temporary directory, effectively emulating chroot(). I also replaced Perl's time() with one that always returned the same answer....