  Mutation testing is an effective but time consuming method for gauging the
quality of a test suite. It functions by repeatedly making changes, called
mutants, to the source code and checking whether the test suite fails (i.e.,
whether the mutant is killed). Recent work has shown cases in which applying
multiple changes, called a higher order mutation, is more difficult to kill
than a single change, called a first order mutation. Specifically, a special
kind of higher order mutation, called a strongly subsuming higher order
mutation (SSHOM), can enable equivalent accuracy in assessing the quality of
the test suite with fewer executions of tests. Little is known about these
SSHOMs, as they are difficult to find. Our goal in this research is to identify
a faster, more reliable method for finding SSHOMs in order to characterize them
in the future. We propose an approach based on variational execution to find
SSHOMs. Preliminary results indicate that variational execution performs better
than the existing genetic algorithm in terms of speed and completeness of
results. Out of a set of 33 first order mutations, our variational execution
approach finds all 38 SSHOMs in 4.5 seconds, whereas the genetic algorithm only
finds 36 of the 38 SSHOMs in 50 seconds.
