That seems like a good idea to me. Why wouldn't this be a reasonable alternative to keeping track of a test count:

use Test::More 'declare_done';
# tests here....
done_testing();
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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.