@Override
    public void execute(FunctionContext context) {
      try {
        Object arg = context.getArguments();
        if (arg != null && arg instanceof Map) {
          context.getResultSender().lastResult("ok");
        } else {
          throw new IllegalArgumentException("dummy");
        }
      } catch (Exception e) {
        context.getResultSender().sendException(e);
      }
    }
This tests make sure that, in case of LonerDistributedSystem we dont get ClassCast Exception.
Just making sure that the function executed on lonerDistribuedSystem
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/execute/MemberFunctionExecutionDUnitTest.java