  Runtime enforcers can be used to ensure that running applications satisfy
desired correctness properties. Although runtime enforcers that are
correct-by-construction with respect to abstract behavioral models are
relatively easy to specify, the concrete software enforcers generated from
these specifications may easily introduce issues in the target application.
Indeed developers can generate test suites to verify the functional behavior of
the enforcers, for instance exploiting the same models used to specify them.
However, it remains challenging and tedious to verify the behavior of enforcers
in terms of non-functional performance characteristics. This paper describes a
practical approach to reveal runtime enforcers that may introduce
inefficiencies in the target application. The approach relies on a combination
of automatic test generation and runtime monitoring of multiple key performance
indicators. We designed our approach to reveal issues in four indicators for
mobile systems: responsiveness, launch time, memory, and energy consumption.
Experimental results show that our approach can detect performance issues that
might be introduced by automatically generated enforcers.
