### Question:
Utils { public static String getTimeAgoString(Period period) { checkNotNull(period); String output = FORMATTER.print(period); if (Strings.isNullOrEmpty(output)) { return "--"; } return output; }  static DateTime receiverTimeToDateTime(long deltaInSeconds); static Date receiverTimeToDate(long delta); static String getTimeAgoString(Period period); static String getTimeString(long timeDeltaMS); static List<GlucoseDataSet> mergeGlucoseDataRecords(List<SensorGlucoseValueEntry> egvRecords,
                                                               List<SensorEntry> sensorRecords); static String bytesToHex(byte[] bytes); static final DateTime DEXCOM_EPOCH; }### Answer:
@Test public void testGetTimeAgoString_ZeroDelta() { DateTime now = new DateTime(); assertThat(Utils.getTimeAgoString(new Period(now, now)), is("0 seconds ago")); }
@Test public void testGetTimeAgoString_SecDelta() { DateTime now = new DateTime(); assertThat(Utils.getTimeAgoString(new Period(now, now.plusSeconds(1))), is("1 seconds ago")); }
@Test public void testGetTimeAgoString_DayDelta() { DateTime now = new DateTime(); assertThat(Utils.getTimeAgoString(new Period(now, now.plusDays(1))), is("1 days ago")); }
@Test public void testGetTimeAgoString_Multiple() { DateTime now = new DateTime(); assertThat(Utils.getTimeAgoString(new Period(now, now.plusMonths(1).plusDays(1).plusSeconds(3))), is("3 seconds, 1 days, and 1 months ago")); }