BufferSpiller { public SpilledBufferOrEventSequence rollOver() throws IOException { return rollOverInternal(false); } BufferSpiller(IOManager ioManager, int pageSize); void add(BufferOrEvent boe); SpilledBufferOrEventSequence rollOver(); SpilledBufferOrEventSequence rollOverWithNewBuffer(); void close();  }
@Test public void testRollOverEmptySequences() { try { assertNull(spiller.rollOver()); assertNull(spiller.rollOver()); assertNull(spiller.rollOver()); } catch (Exception e) { e.printStackTrace(); fail(e.getMessage()); } }