@Override
              public int compare(Path o1, Path o2) {
                Matcher m1 = BackupFileManager.versionFilenamePattern.matcher(o1.getFileName().toString());
                Matcher m2 = BackupFileManager.versionFilenamePattern.matcher(o2.getFileName().toString());
                m1.find();
                m2.find();
                int v1 = Integer.parseInt(m1.group(1));
                int v2 = Integer.parseInt(m2.group(1));
                return v1 - v2;
              }
Updates a collection of {@link Account}s through {@link HelixAccountService}, and verifies that the
{@link Account}s have been successfully updated, so they can be queried through {@link HelixAccountService}.
@param accounts A collection of {@link Account}s to update through {@link HelixAccountService}.
ambry-account/src/test/java/com/github/ambry/account/HelixAccountServiceTest.java