private ZNRecord makeZNRecordWithSimpleField(ZNRecord oldRecord, String key, String value) {
    ZNRecord zNRecord = oldRecord == null ? new ZNRecord(String.valueOf(System.currentTimeMillis())) : oldRecord;
    if (key != null && value != null) {
      zNRecord.setSimpleField(key, value);
    }
    return zNRecord;
  }
Add or update a {@link ZNRecord} to include a simple field with the given key and value. If the supplied
{@link ZNRecord} is null, a new {@link ZNRecord} will be created.
@param oldRecord A {@link ZNRecord} to add or update its simple field. {@code null} indicates to create a
                 new {@link ZNRecord}.
@param key The key for the simple field.
@param value The value for the simple field.
@return A {@link ZNRecord} including a simple field with the given key and value.
ambry-account/src/test/java/com/github/ambry/account/HelixAccountServiceTest.java