public int getMaxSnapshotID() {
    return ((1 << SNAPSHOT_ID_BIT_WIDTH) - 1);
  }
@Test
  public void testValidateSnapshotIDWidth() throws Exception {
    FSDirectory fsdir = mock(FSDirectory.class);
    SnapshotManager snapshotManager = new SnapshotManager(new Configuration(),
        fsdir);
    Assert.assertTrue(snapshotManager.
        getMaxSnapshotID() < Snapshot.CURRENT_STATE_ID);
  }