  Regression testing ensures that a software system when it evolves still
performs correctly and that the changes introduce no unintended side-effects.
However, the creation of regression test cases that show divergent behavior
needs a lot of effort. A solution is the idea of shadow symbolic execution,
originally implemented based on KLEE for programs written in C, which takes a
unifed version of the old and the new program and performs symbolic execution
guided by concrete values to explore the changed behavior. In this work, we
apply the idea of shadow symbolic execution to Java programs and, hence,
provide an extension of the Java PathFinder (JPF) project to perform shadow
symbolic execution on Java bytecode. The extension has been applied on several
subjects from the JPF test classes where it successfully generated test inputs
that expose divergences relevant for regression testing.
