old_contents: import os
  import pytest
  
  import pandas
  from skan import pipe
  
  @pytest.fixture
  def image_filename():
      rundir = os.path.abspath(os.path.dirname(__file__))
      datadir = os.path.join(rundir, 'data')
      return os.path.join(datadir, 'retic.tif')
  
  
  def test_pipe(image_filename):
      data = pipe.process_images([image_filename], 'fei', 5e-8, 0.1, 0.075,
                                 'Scan/PixelHeight')
      assert type(data) == pandas.DataFrame
      assert data.shape[0] > 0
  
new_contents: import os
  import pytest
  import tempfile
  
  import pandas
  from skan import pipe
  
  @pytest.fixture
  def image_filename():
      rundir = os.path.abspath(os.path.dirname(__file__))
      datadir = os.path.join(rundir, 'data')
      return os.path.join(datadir, 'retic.tif')
  
  
  def test_pipe(image_filename):
      data = pipe.process_images([image_filename], 'fei', 5e-8, 0.1, 0.075,
                                 'Scan/PixelHeight')
      assert type(data) == pandas.DataFrame
      assert data.shape[0] > 0
  
  
  def test_pipe_figure(image_filename):
      with tempfile.TemporaryDirectory() as tempdir:
          data = pipe.process_images([image_filename], 'fei', 5e-8, 0.1, 0.075,
                                     'Scan/PixelHeight',
                                     save_skeleton='skeleton-plot-',
                                     output_folder=tempdir)
          assert type(data) == pandas.DataFrame
          assert data.shape[0] > 0
          assert os.path.exists(os.path.join(tempdir,
                                             'skeleton-plot-' +
                                             image_filename[:-4] +
                                             '.png'))
  
subject: Add test for saving skeleton image