On the Effect of Object Redundancy Elimination in Randomly Testing Collection Classes

In this paper, we analyze the effect of reducing object redundancy in random testing, by comparing the Randoop random testing tool with a version of the tool that disregards tests that only produce objects that have been previously generated by other tests. As a side effect, this variant also identifies methods in the software under test that never participate in state changes, and uses these more heavily when building assertions. Our evaluation of this strategy concentrates on collection classes, since in this context of object-oriented implementations that describe stateful objects obbeying complex invariants, object variability is highly relevant. Our experimental comparison takes the main data structures in java.util, and shows that our object redundancy reduction strategy has an important impact in testing collections, measured in terms of code coverage and mutation killing.