### Question:
DisplayUtils { public static String formatAccountAge(long durationMillis) { durationMillis = Math.max(0, durationMillis); String day = Res.get("time.day").toLowerCase(); String days = Res.get("time.days"); String format = " d\' " + days + "\'"; return StringUtils.strip(StringUtils.replaceOnce(DurationFormatUtils.formatDuration(durationMillis, format), " 1 " + days, " 1 " + day)); }  static String formatDateTime(Date date); static String formatDateTimeSpan(Date dateFrom, Date dateTo); static String formatTime(Date date); static String formatDate(Date date); static String formatAccountAge(long durationMillis); static String booleanToYesNo(boolean value); static String formatVolume(Offer offer, Boolean decimalAligned, int maxNumberOfDigits); static String formatVolume(Offer offer, Boolean decimalAligned, int maxNumberOfDigits, boolean showRange); static String formatVolume(Volume volume); static String formatVolumeWithCode(Volume volume); static String formatVolumeLabel(String currencyCode); static String formatVolumeLabel(String currencyCode, String postFix); static String getDirectionWithCode(OfferPayload.Direction direction, String currencyCode); static String getDirectionBothSides(OfferPayload.Direction direction, String currencyCode); static String getDirectionForBuyer(boolean isMyOffer, String currencyCode); static String getDirectionForSeller(boolean isMyOffer, String currencyCode); static String getDirectionForTakeOffer(OfferPayload.Direction direction, String currencyCode); static String getOfferDirectionForCreateOffer(OfferPayload.Direction direction, String currencyCode); static String formatAmount(Offer offer, CoinFormatter coinFormatter); static String formatAmount(Offer offer,
                                      int decimalPlaces,
                                      boolean decimalAligned,
                                      int maxPlaces,
                                      CoinFormatter coinFormatter); static String formatPrice(Price price, Boolean decimalAligned, int maxPlaces); static String getFeeWithFiatAmount(Coin makerFeeAsCoin,
                                              Optional<Volume> optionalFeeInFiat,
                                              CoinFormatter formatter); static Coin parseToCoinWith4Decimals(String input, CoinFormatter coinFormatter); static boolean hasBtcValidDecimals(String input, CoinFormatter coinFormatter); static Coin reduceTo4Decimals(Coin coin, CoinFormatter coinFormatter);  }### Answer:
@Test public void testFormatAccountAge() { assertEquals("0 days", DisplayUtils.formatAccountAge(TimeUnit.HOURS.toMillis(23))); assertEquals("0 days", DisplayUtils.formatAccountAge(0)); assertEquals("0 days", DisplayUtils.formatAccountAge(-1)); assertEquals("1 day", DisplayUtils.formatAccountAge(TimeUnit.DAYS.toMillis(1))); assertEquals("2 days", DisplayUtils.formatAccountAge(TimeUnit.DAYS.toMillis(2))); assertEquals("30 days", DisplayUtils.formatAccountAge(TimeUnit.DAYS.toMillis(30))); assertEquals("60 days", DisplayUtils.formatAccountAge(TimeUnit.DAYS.toMillis(60))); }