Nice illustration. Most tests are as simple as those you have shown. Tests are meant to be very simple. Test the value of a function, test the type of the class prodcued by your constructor, test that your function breaks nicely for stupid inputs - by feeding it stupid inputs and looking at the results.
Take a look at some of the test code on CPAN - the few that I've looked at consist of strings of simple tests. The hardest tests are those which depend on something outside your module.-- Anthony Staines