@Override
      public Object call() {
        CacheTransactionManager mgr = getCache().getCacheTransactionManager();
        mgr.addListener(new ClientTxListener());
        try {
          mgr.setWriter(new ClientTxWriter());
          fail("expected exception not thrown");
        } catch (IllegalStateException ignored) {
        }
        Region<CustId, Customer> pr = getGemfireCache().getRegion(CUSTOMER);
        pr.getAttributesMutator().addCacheListener(new ClientListener());
        pr.getAttributesMutator().setCacheWriter(new ClientWriter());
        return null;
      }
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