@Override
  public void flush() throws IOException {
    mLocalOutputStream.flush();
  }
@Test
  @PrepareForTest(OBSOutputStream.class)
  public void testFlush() throws Exception {
    PowerMockito.whenNew(BufferedOutputStream.class)
        .withArguments(any(DigestOutputStream.class)).thenReturn(mLocalOutputStream);
    OBSOutputStream stream = new OBSOutputStream("testBucketName", "testKey", mObsClient,
        sConf.getList(PropertyKey.TMP_DIRS));
    stream.flush();
    stream.close();
    Mockito.verify(mLocalOutputStream).flush();
  }