@Test
  public void testUpdateAccount() throws Exception {
    // first, create NUM_REF_ACCOUNT accounts through the tool
    createOrUpdateAccountsAndWait(idToRefAccountMap.values());
    assertAccountsInAccountService(idToRefAccountMap.values(), NUM_REF_ACCOUNT, accountService);

    // then, update the name of all the accounts again through the tool
    String accountNameAppendix = "-accountNameAppendix";
    String containerNameAppendix = "-containerNameAppendix";
    Collection<Account> updatedAccounts = new ArrayList<>();
    for (Account account : accountService.getAllAccounts()) {
      AccountBuilder accountBuilder = new AccountBuilder(account).name(account.getName() + accountNameAppendix);
      for (Container container : account.getAllContainers()) {
        accountBuilder.addOrUpdateContainer(
            new ContainerBuilder(container).setName(container.getName() + containerNameAppendix).build());
      }
      updatedAccounts.add(accountBuilder.build());
    }
    createOrUpdateAccountsAndWait(updatedAccounts);
    assertAccountsInAccountService(updatedAccounts, NUM_REF_ACCOUNT, accountService);
  }
Tests updating {@link Account}s to {@code ZooKeeper}, where the {@link Account}s to update already exist.
@throws Exception Any unexpected exception.
ambry-tools/src/integration-test/java/com/github/ambry/account/AccountUpdateToolTest.java