@Override
      public Object call() {
        RedundantListener l =
            (RedundantListener) getCache().getCacheTransactionManager().getListeners()[0];
        return l.invoked;
      }
test has a client, two accessors and a datastore pool connects to two accessors. we then close
the server in first accessor and verify failover
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/ClientServerTransactionDUnitTest.java