Object Coverage Criteria for Supporting Object-oriented Testing

Code coverage criteria are widely used in object-oriented (OO) domains as test quality indicators. However, these criteria are based on the procedural point of view, and therefore, do not address the specific features of OO programs. In this article, we extend the code coverage criteria and introduce a new set of criterion, called “object coverage criteria”, which cope with OO features like object instantiation, inheritance, polymorphism, and dynamic binding. Unlike previous criteria, the new criteria regard the actual type of the object under test and some inherited codes from the parent/ancestor classes that represent the object’s states and behaviors. The new criteria have been implemented in a prototype tool called OCov4J for the Java language. Using this tool and conducting an empirical study on totally 270 classes (with about 50k lines of code without blank lines and comments) from several large and widely used open source projects, we have found a considerable positive correlation between the object coverage level (defined via the new proposed criteria) and the number of detected specific OO failures. Not only the proposed criteria provide ease of use, high automation, and low execution cost, they can effectively be applied to real world object oriented programs.