@Test public void testGetSignature4Sort() { final BookDO book = new BookDO(); book.setSignature(null); assertNull(book.getSignature4Sort()); book.setSignature(""); assertEquals("", book.getSignature4Sort()); book.setSignature("W"); assertEquals("W", book.getSignature4Sort()); book.setSignature("WT-"); assertEquals("WT-", book.getSignature4Sort()); book.setSignature("WT-23a"); assertEquals("WT-00023a", book.getSignature4Sort()); book.setSignature("WT-2-5"); assertEquals("WT-00002-00005", book.getSignature4Sort()); }