simpler example

timhoffm · timhoffm · commit 490d2bc009de · 2018-10-18T23:37:14.000+02:00
diff --git a/doc/devel/testing.rst b/doc/devel/testing.rst
@@ -152,12 +152,11 @@ tests it::
    from matplotlib.testing.decorators import image_comparison
    import matplotlib.pyplot as plt
 
-   @image_comparison(baseline_images=['hexbin_empty'], remove_text=True,
+   @image_comparison(baseline_images=['line_dashes'], remove_text=True,
                      extensions=['png'])
-   def test_hexbin_empty():
-       # From #3886: creating hexbin from empty dataset raises ValueError
-       ax = plt.gca()
-       ax.hexbin([], [])
+   def test_line_dashes():
+       fig, ax = plt.subplots()
+       ax.plot(range(10), linestyle=(0, (3, 3)), lw=5)
 
 The first time this test is run, there will be no baseline image to compare
 against, so the test will fail.  Copy the output images (in this case
diff --git a/lib/matplotlib/testing/decorators.py b/lib/matplotlib/testing/decorators.py
@@ -368,7 +368,7 @@ def image_comparison(baseline_images, extensions=None, tol=0,
         either as a parameter or with pytest.mark.usefixtures. This value is
         only allowed when using pytest.
 
-    extensions : [ None | list ]
+    extensions : None or list of str
         The list of extensions to test, e.g. ``['png', 'pdf']``.
 
         If *None*, defaults to all supported extensions: png, pdf, and svg.
