@Test
public void testPlusDays()
{

    DateTimeUnit dateTimeUnit = new DateTimeUnit( 2014, 12, 30 );
    DateTimeUnit testDateTimeUnit = calendar.plusDays( dateTimeUnit, -1 );
    assertEquals( 2014, testDateTimeUnit.getYear() );
    assertEquals( 12, testDateTimeUnit.getMonth() );
    assertEquals( 29, testDateTimeUnit.getDay() );
    dateTimeUnit = new DateTimeUnit( 2014, 1, 1 );
    testDateTimeUnit = calendar.plusDays( dateTimeUnit, - 1 );
    assertEquals( 2013, testDateTimeUnit.getYear() );
    assertEquals( 12, testDateTimeUnit.getMonth() );
    assertEquals( 30, testDateTimeUnit.getDay() );
}