Common use of Threats to Validity Clause in Contracts

Threats to Validity. Due to the randomness of Randoop, the numbers in third to last columns of Table IV can be varied each time an experiment is performed, although in our experience the gap was not significant. In addition, these numbers are also affected by the limitations of our tool. For example, we found that XMLUnit, a tool we used to check the isomorphism between inputs, occasionally categorized isomorphic inputs as non-isomorphic due to the order sensitiveness of the tool in comparing object graphs. Lastly, our experimental results are confined to a single subject Ant, and we need to conduct experiments with more subjects to generalize the results we obtained to other cases.