A New Method for Estimating the Testability of Polymorphism in Class Hierarchy

Abstract

Software testing is one of the most common ways for assuring quality of software system, and software testability be also recognized as new part of the software quality at the same time. Conventional software testing methods are divided into two categories: static testing and dynamic testing. Most of testing methodologies fall into the category of dynamic test, due to the face that more information can be derived during programs execution. On the contrary, in object-oriented software test, the feature of inheritance and polymorphism produce new testing obstacle during dynamic testing. Our research in this paper will propose a tester perspective to assess the polymorphism in design stage and this way also provide useful information for developer to probe into the fault that is hidden from test in early stage. In addition, from our polymorphism RATO model, we recognized a new factor of testability in design stage that is referred to as reachability. We think that the main contribution of this paper is providing an alternative tester perspective for developer and let developer can estimate the polymorphic behavior in class inheritance hierarchy that may cause of test obstacle at design phase. At the same time, this is first literature to propose the polymorphism RATO model to model polymorphic behavior, and use it as basis of analytical unit to decompose inheritance class hierarchy. Besides, we overcome the interdiction of lack of testing information during design stage in the past. The metric of testability on polymorphism, generated by the polymorphism RATO model, can reveal defects that hide at design stage in class hierarchy, it can provide most early information for developer on modify, redesign the system and find another way to fix these defect as well.