In this idea paper, we propose a novel way for improving the testing of program changes via symbolic execution. At a high-level, our technique runs two different program versions in the same symbolic execution instance, with the old version effectively shadowing the new one. In this way, the technique can exploit precise dynamic value information to effectively drive execution toward the behaviour that has changed from one version to the next. We discuss the main challenges and opportunities of this approach in terms of pruning and prioritising path exploration, mapping elements across versions, and sharing common symbolic state between versions.
Conference talk at ICSE NIER 2014.