Testing Polymorphic Relationships

As we move from developing procedure-oriented to object-oriented programs, the complexity traditionally found in functions and procedures is moving to the connections among components. Different faults occur when components are integrated to form higher level structures that aggregate the behavior and state of the components. Consequently, we need to place more effort on testing the connections among components. Although object-oriented technologies provide abstraction mechanisms for building components that can then be integrated to form applications, it also adds new compositional relations that can contain faults, which are most properly found during integration testing. This paper describes techniques for analyzing and testing the polymorphic relationships that occur in object-oriented software. The techniques adapt traditional data flow coverage criteria to consider definitions and uses among state variables of classes, particularly in the presence of inheritance and polymorphic overriding of state variables and methods. The application of these techniques can result in an increased ability to find faults and to create overall higher quality software.