@Override
  public FileChecksum getFileChecksum(Path f, long length) {
    return null;
  }
@Test
  public void testFileChecksum() throws Exception {
    final Path p = new Path("har://file-localhost/foo.har/file1");
    try (HarFileSystem harfs = new HarFileSystem()) {
      assertThat(harfs.getFileChecksum(p)).isNull();
    }
  }