@Override
  public long getPreferredBlockSize() {
    return HeaderFormat.getPreferredBlockSize(header);
  }
@Test
  public void testPreferredBlockSize () {
    replication = 3;
    preferredBlockSize = 128*1024*1024;
    INodeFile inf = createINodeFile(replication, preferredBlockSize);
   assertEquals("True has to be returned in this case", preferredBlockSize,
        inf.getPreferredBlockSize());
 }