Incremental testing of object-oriented class structures

Abstract

Although there is much interest in creating libraries of well-designed, thoroughly-tested classes that can be confidently reused for many applications, few class testing techniques have been developed. In this paper, we present a class testing technique that exploits the hierarchical nature of the inheritance relation to test related groups of classes by reusing the testing information for a parent class to guide the testing of a subclass. We initially test base classes having no parents by designing a test suite that tests each member function individually and also tests the interactions among member functions. To design a test suite for a subclass, our algorithm incrementally updates the history of its parent to reflect both the modified, inherited attributes and the subclass's newly defined attributes. Only those new attributes or affected, inherited attributes are tested and the parent class' test suites are reused, if possible, for the testing. Inherited attributes are retested in their new context in a subclass by testing their interactions with the subclass's newly defined attributes. We have incorporated a data flow tester into Free Software Foundation, Inc's C++ compiler© and are using it for our experimentation.