long size() {
    return directories.size();
  }
@Test
  public void testDeletePerfectCache() throws Throwable {
    // run a larger scale test. Also use the ordering we'd expect for a sorted
    // listing, which we implement by sorting the paths
    List<CopyListingFileStatus> statusList = buildStatusList();
    // cache is bigger than the status list
    tracker = new DeletedDirTracker(statusList.size());

    AtomicInteger deletedFiles = new AtomicInteger(0);
    AtomicInteger deletedDirs = new AtomicInteger(0);
    deletePaths(statusList, deletedFiles, deletedDirs);
    assertEquals(0, deletedFiles.get());
  }