@Override
  public void flush() throws IOException {
    writer.force(false);
  }
@Test
    public void testFlush() throws Exception {
        DistributedLogManager dlm = mock(DistributedLogManager.class);
        AppendOnlyStreamWriter writer = mock(AppendOnlyStreamWriter.class);
        DLOutputStream out = new DLOutputStream(dlm, writer);

        out.flush();
        verify(writer, times(1)).force(eq(false));
    }