I have a unit test called TestMakeAValidCall(). It tests my phone app making a valid call.
I am about to write another test called TestShowCallMe
A unit vs. module....we also think tests should depend on reusable methods as well and should test at an api level testing integration of classes. Many just tests a single class but many bugs are at that integration between the class level. We also use verifydesign to guarantee the api does not depend on implementation. This allows you to refactor the whole component/module without touching a test(and we went through that once actually and it worked great). Of course, any architectural changes force you to refactor the tests but at least design changes in the module don't cause test refactor work(unless you change the behavior of the api of course implicitly like firing more events than you used to but that "would" be an api change anyways).