In situations where you have deep trees of classes, there is a common situation
in which you test a module 4 or 5 subclasses down, which should follow the
correct behaviour of not just the subclass, but of all the parent classes.

This should be done to ensure that the implementation of a subclass has not
somehow "broken" the object's behaviour in a more general sense.

Test::Object is a testing package designed to allow you to easily test what you
believe is a valid object against the expected behaviour of all of the classes
in its inheritance tree in one single call.