ITC is done after the object has been tested at the (unit)
object level. Testing the object at the global level, i.e., the
range of all possible parents from whom the object can
inherit methods, is needed. Testing the inheritance of an
object must be done if the various forms exist in that object:
multilevel (inheritance from a parent that already inherited
from its own parent) or multiple (inheritance from more than
single parent) or hierarichal (inherited by more than one
class from one parent class). All inherited methods in the
scope of one object have to be considered for
testing/retesting based on the nature of their use.