@Override
    public Collection<String> filesUnderSnapshot(final FileSystem workingFs, final Path snapshotDir)
      throws IOException {
      Collection<String> files = new HashSet<>();
      files.addAll(SnapshotReferenceUtil.getHFileNames(conf, workingFs, snapshotDir));
      return files;
    }
Test that we correctly reload the cache, filter directories, etc.
hbase-server/src/test/java/org/apache/hadoop/hbase/master/snapshot/TestSnapshotFileCache.java