@VisibleForTesting
  public BlockPlacementPolicy getBlockPlacementPolicy() {
    return placementPolicies.getPolicy(CONTIGUOUS);
  }
@Test
  public void testUseDelHint() {
    DatanodeStorageInfo delHint = new DatanodeStorageInfo(
        DFSTestUtil.getLocalDatanodeDescriptor(), new DatanodeStorage("id"));
    List<DatanodeStorageInfo> moreThan1Racks = Arrays.asList(delHint);
    List<StorageType> excessTypes = new ArrayList<>();
    BlockPlacementPolicyDefault policyDefault =
        (BlockPlacementPolicyDefault) bm.getBlockPlacementPolicy();
    excessTypes.add(StorageType.DEFAULT);
    Assert.assertTrue(policyDefault.useDelHint(delHint, null, moreThan1Racks,
        null, excessTypes));
    excessTypes.remove(0);
    excessTypes.add(StorageType.SSD);
    Assert.assertFalse(policyDefault.useDelHint(delHint, null, moreThan1Racks,
        null, excessTypes));
  }