### Question:
PuzzleManager extends AbstractMongoManager { public Puzzle getRandomPuzzle(User user) { int index = CommonUtil.getRandomInt(dataList.size()); return dataList.get(index); } private  PuzzleManager(); static PuzzleManager getInstance(); void reload(); Puzzle getRandomPuzzle(User user); Puzzle getPuzzleByIndex(int index); ArrayList<Puzzle> getPuzzles(); void addPuzzle(String question, String answer);  }### Answer:
@Test public void testGetRandomPuzzle() { Puzzle puzzle = PuzzleManager.getInstance().getRandomPuzzle(null); System.out.println(puzzle); assertNotNull(puzzle); }