Template method test pattern

How to test abstract classes is an area of testing that is not paid much attentionto. Abstract classes cannot be instantiated and therefore standard execution-based test strategies are not applicable.In this paper, we consider a special case of an abstract class, namely oneproduced by the Template Method pattern. This pattern results in an abstractclass, with a concrete template method and one or more abstract primitiveoperations, and one or more subclasses, implementing the primitive operationsspecifically for each subclass.How should we test an instance of the Template Method pattern? Testingthe concrete template method by testing the abstract class is impossible. Testingan instance of the Template Method pattern by testing the template method inall of the subclasses individually is error-prone in the long run.This paper presents a structured approach to test instances of the TemplateMethod pattern in an elegant way using the Abstract Factory pattern. Fur-thermore, we introduce the new conceptsemi-abstract methodto reason aboutconcrete methods that depend on abstract operations. We formalize the patternand demonstrate the approach at work using an example program