That seems like a good idea to me. Why wouldn't this be a reasonable alternative to keeping track of a test count:
in reply to Re^3: Toggling test plans with vim
in thread Toggling test plans with vim
I've declared that my plan is to declare when I'm done testing. At the end of the test script, I do just that. Now, if the script exits early and done_testing() hasn't be called, we know there was a problem, and we know where it is, because we know the last test that was run.
use Test::More 'declare_done';
# tests here....