I can't speak for the module author, but I'd second guess that the purpose behind some specified plan i.e. a possible answer to your 1st question, is to give yourself (and Test::More) some level of confidence that you thought things thro' prior to implementing the tests.

Moreover, I'd refer you to Perl Testing - A Developers Notebook.

Personally, I've found it [specifying the expected number of tests] useful on 3 counts:

• It gives me a higher degree of confidence that I know what's going to be tested and have planned accordingly.
• Twice now I've planned to run n tests, only to find m have been run instead and thus (when run with TEST_VERBOSE=1) I was, in both cases, able to identify the errant test(s) and correct the situation (by fixing the bug that prevented their execution ... c/w adjusting the number of test to be run, of course:-))).
• Finally, as a metric - to keep management 'happy'.