old_contents: from contextlib import contextmanager
  import os
  import tempfile
  import unittest
  
  from matplotlib.pyplot import Artist, savefig
  from shapely.geometry import Polygon, LineString, Point
  
  from geopandas import GeoSeries
  
  
  @contextmanager
  def get_tempfile():
      f, path = tempfile.mkstemp()
      try:
          yield path
      finally:
          try:
              os.remove(path)
          except:
              pass
  
  class TestSeriesPlot(unittest.TestCase):
  
      def setUp(self):
          self.t1 = Polygon([(0, 0), (1, 0), (1, 1)])
          self.t2 = Polygon([(1, 0), (2, 1), (2, 1)])
          self.polys = GeoSeries([self.t1, self.t2])
  
      def test_poly_plot(self):
          """ Test plotting a simple series of polygons """
          ax = self.polys.plot()
          self.assertIsInstance(ax, Artist)
          with get_tempfile() as file:
              savefig(file)
  
  if __name__ == '__main__':
      unittest.main()
  
new_contents: import os
  import unittest
  
  from matplotlib.pyplot import Artist, savefig
  from matplotlib.testing.decorators import image_comparison
  from shapely.geometry import Polygon, LineString, Point
  
  from geopandas import GeoSeries
  
  # If set to True, generate images rather than perform tests (all tests will pass!)
  GENERATE_BASELINE = False
  
  BASELINE_DIR = os.path.join(os.path.dirname(__file__), 'baseline_images', 'test_plotting')
  
  def save_baseline_image(filename):
      """ save a baseline image """
      savefig(os.path.join(BASELINE_DIR, filename))
  
  @image_comparison(baseline_images=['poly_plot'], extensions=['png'])
  def test_poly_plot():
      """ Test plotting a simple series of polygons """
      t1 = Polygon([(0, 0), (1, 0), (1, 1)])
      t2 = Polygon([(1, 0), (2, 1), (2, 1)])
      polys = GeoSeries([t1, t2])
      ax = polys.plot()
      assert isinstance(ax, Artist)
      if GENERATE_BASELINE:
          save_baseline_image('poly_plot.png')
  
  if __name__ == '__main__':
      import nose
      nose.runmodule(argv=['-s', '--with-doctest'])
  
subject: Use matplotlib image_comparison to actually compare plot output