Let’s assume for the moment that you’re writing a Perl module or application. You’d like to maintain some level of software quality (or kwalitee), so you’re writing a suite of test scripts. Whether you’re writing them first (good for you for practicing test-driven development!) or the application code is already there, you’ll probably be reaching for Test::Simple, Test::More, or one of the Test2::Suite bundles. With the latter two you’re immediately confronted with a choice: do you count up the number of tests into a plan, or do you forsake that in favor of leaving a done_testing() call at the end of your test script(s)?

There are good arguments for both approaches. When you first start, you probably have no idea how many tests your scripts will contain. After all, a test script can be a useful tool for designing a module’s interface by writing example code that will use it. Your exploratory code would be written as if the module or application was already done, testing it in the way you’d like it to work. Not declaring a plan makes perfect sense in this case; just put done_testing() at the end and get back to defining your tests.

Source: DZone