### Question:
TimeInSecondsToStringConverter extends StringConverter<Number> { @Override public String toString(final Number nValue) { if (nValue == null) { return ""; } return TimeUtils.seconds2TimeString(nValue.intValue()); }  @Override String toString(final Number nValue); @Override Number fromString(final String strValue);  }### Answer:
@Test public void testToString() { assertEquals("", CONVERTER.toString(null)); assertEquals("00:00:00", CONVERTER.toString(0)); assertEquals("00:59:59", CONVERTER.toString(3599)); assertEquals("01:00:00", CONVERTER.toString(3600)); assertEquals("100:00:00", CONVERTER.toString(3600*100)); }