A Fault Model for Subtype Inheritance and Polymorphism

Although program faults are widely studied, there are many aspects of faults that we still do not understand, particularly about OO software. In addition to the simple fact that one important goal during testing is to cause failures and thereby detect faults, a full understanding of the characteristics of faults is crucial to several research areas. The power that inheritance and polymorphism brings to the expressiveness of programming languages also brings a number of new anomalies and fault types. This paper presents a model for the appearance and realization of OO faults and defines and discusses specific categories of inheritance and polymorphic faults. The model and categories can be used to support empirical investigations of object-oriented testing techniques, to inspire further research into objectoriented testing and analysis, and to help improve design and development of object-oriented software.