An Investigation into the Effect of Control and Data Dependence Chain Length on Predicate Testability

The squeeziness of a sequence of program statements captures the loss of information (loss of entropy) caused by its execution. This information loss leads to problems such as failed error propagation. Intuitively, longer more complex statement sequences (more formally, longer paths of dependencies) bring greater squeeze. Using the cost of search-based test data generation as a measure of lost information, we investigate this intuition. Unexpectedly, we find virtually no correlation between dependence path length and information loss. Thus our study represents an (unexpected) negative result.Moreover, looking through the literature, this finding is in agreement with recent work of Masri and Podgurski. As such, our work replicates a negative result. More precisely, it provides a conceptual, generalization and extension replication. The replication falls into the category of a conceptual replication in that different methods are used to address a common problem, and into the category of generalization and extension in that we sample a different population of subjects and more rigorously consider the resulting data. Specifically, while Masri and Podgurski only informally observed the lack of a connection, we rigorously assess it using a range of statistical models.