Reported in https://github.com/google/guava/issues/3086#issuecomment-378523615

Needs a fix like https://github.com/google/guava/commit/8f22dbc8ea0c1abdf044846057f6df8201ee9961
rootDir.getFileSystem().close();
  }
  public void testFileTraverser_emptyDirectory() throws Exception {
    assertThat(MoreFiles.fileTraverser().breadthFirst(rootDir)).containsExactly(rootDir);
  }
  public void testFileTraverser_nonExistingFile() throws Exception {
    Path file = rootDir.resolve("file-that-doesnt-exist");
    assertThat(MoreFiles.fileTraverser().breadthFirst(file)).containsExactly(file);
  }
  public void testFileTraverser_file() throws Exception {
    Path file = newFile("some-file");
    assertThat(MoreFiles.fileTraverser().breadthFirst(file)).containsExactly(file);
  }
  public void testFileTraverser_singleFile() throws Exception {
    Path file = newFile("some-file");
    assertThat(MoreFiles.fileTraverser().breadthFirst(rootDir)).containsExactly(rootDir, file);
  }
  public void testFileTraverser_singleDirectory() throws Exception {
    Path file = newDir("some-dir");
    assertThat(MoreFiles.fileTraverser().breadthFirst(rootDir)).containsExactly(rootDir, file);
  }
  public void testFileTraverser_multipleFilesAndDirectories() throws Exception {
    Path fileA = newFile("file-a");
    Path fileB = newFile("file-b");
    Path dir1 = newDir("dir-1");
    Path dir2 = newDir("dir-2");
    assertThat(MoreFiles.fileTraverser().breadthFirst(rootDir))
        .containsExactly(rootDir, fileA, fileB, dir1, dir2);
  }
  public void testFileTraverser_multipleDirectoryLayers_breadthFirstStartsWithTopLayer()