class_docstr: Test the area helpers.
docstr: Test the bz2 file unzipping techniques.
code: def test_unzip_file(self, mock_popen, mock_bz2):
      """Test the bz2 file unzipping techniques."""
      process_mock = mock.Mock()
      attrs = {
          "communicate.return_value": (b"output", b"error"),
          "returncode": 0,
      }
      process_mock.configure_mock(**attrs)
      mock_popen.return_value = process_mock
  
      bz2_mock = mock.MagicMock()
      bz2_mock.__enter__.return_value.read.return_value = b"TEST"
      mock_bz2.return_value = bz2_mock
  
      filename = "tester.DAT.bz2"
      whichstr = "satpy.readers.utils.which"
      segment = 3
      segmentstr = str(segment).zfill(2)
      # no pbzip2 installed with prefix
      with mock.patch(whichstr) as whichmock:
          whichmock.return_value = None
          new_fname = hf.unzip_file(filename, prefix=segmentstr)
          assert bz2_mock.__enter__.return_value.read.called
          assert os.path.exists(new_fname)
          assert os.path.split(new_fname)[1][0:2] == segmentstr
          if os.path.exists(new_fname):
              os.remove(new_fname)
      # pbzip2 installed without prefix
      with mock.patch(whichstr) as whichmock:
          whichmock.return_value = "/usr/bin/pbzip2"
          new_fname = hf.unzip_file(filename)
          assert mock_popen.called
          assert os.path.exists(new_fname)
          assert os.path.split(new_fname)[1][0:2] != segmentstr
          if os.path.exists(new_fname):
              os.remove(new_fname)
  
      filename = "tester.DAT"
      new_fname = hf.unzip_file(filename)
      assert new_fname is None
  
imports: import os
  import unittest
  from datetime import datetime
  from unittest import mock
  import dask.array
  import numpy
  import numpy.testing
  import pyresample.geometry
  import pytest
  import xarray
  from fsspec.implementations.memory import MemoryFile, MemoryFileSystem
  from pyproj import CRS
  from satpy.readers import FSFile
  from satpy.readers import utils
label_desc: Use image node_id 9 for calling the TestHelpers obj's underlying member method code with example usage: obj.test_unzip_file(mock_popen, mock_bz2) without return types