DummyMessagePrinter implements MessagePrinter { public static MessagePrinter getInstance() { if (null == instance) { synchronized (DummyMessagePrinter.class) { if (null == instance) { instance = new DummyMessagePrinter(); } return instance; } } return instance; }  static MessagePrinter getInstance(); @Override void print(String format, Object... args); @Override void println(); @Override void println(String format, Object... args); @Override void flush();  }
@Test public void testGetInstance() { assertNotNull(DummyMessagePrinter.getInstance()); }