private long numberOfChunks(Map map) {
    return map.keySet().parallelStream().filter(k -> (k instanceof ChunkKey)).count();
  }
Test what happens a file rename is aborted in the middle due to the a cache closed exception.
The next member that uses those files should be able to clean up after the partial rename.
geode-lucene/src/test/java/org/apache/geode/cache/lucene/internal/filesystem/FileSystemJUnitTest.java