This is not a requirement, its just an assumption. You can write your own test cases.
The skeleton just makes the layout in the “easy way” that makes dummy functions for all of your dummy functions in your class.
Besides,
phpunit --skeleton-test MyClass MyClass.class.php
You can do what you want.
Usage: phpunit [switches] UnitTest [UnitTest.php]
phpunit [switches] <directory>
--skeleton-class Generate Unit class for UnitTest in UnitTest.php.
--skeleton-test Generate UnitTest class for Unit in Unit.php.
, , , , , , .