An empirical study into class testability

In this paper we investigate factors of the testability of object-oriented software systems. The starting point is given by a study of the literature to obtain both an initial model of testability and existing object-oriented metrics related to testability. Subsequently, these metrics are evaluated by means of five case studies of commercial and open source Java systems for which JUnit test cases exist. The goal of this paper is to identify and evaluate a set of metrics that can be used to assess the testability of the classes of a Java system.