@Test
  public void testStartUpWithMetadataExists() throws Exception {
    // pre-populate account metadata in ZK.
    writeAccountsToHelixPropertyStore(idToRefAccountMap.values(), false);
    // When start, the helixAccountService should get the account metadata.
    accountService = mockHelixAccountServiceFactory.getAccountService();
    assertAccountsInAccountService(idToRefAccountMap.values(), NUM_REF_ACCOUNT, accountService);
  }
Tests starting up a {@link HelixAccountService}, when the corresponding {@code ZooKeeper} has account metadata
already stored on it.
@throws Exception Any unexpected exception.
ambry-account/src/test/java/com/github/ambry/account/HelixAccountServiceTest.java