Add tests for output-base-name

Author: asmeurer

lib/matplotlib/tests/test_sphinxext.py

@@ -97,6 +97,9 @@ def plot_directive_file(num):
     assert filecmp.cmp(range_6, plot_file(17))
     # plot 22 is from the range6.py file again, but a different function
     assert filecmp.cmp(range_10, img_dir / 'range6_range10.png')
+    # plots 23 and 24 use a custom base name with {counter}
+    assert filecmp.cmp(range_4, img_dir / 'custom-base-name-18.png')
+    assert filecmp.cmp(range_6, img_dir / 'custom-base-name-19.png')
 
     # Modify the included plot
     contents = (tmp_path / 'included_plot_21.rst').read_bytes()

lib/matplotlib/tests/tinypages/some_plots.rst

@@ -174,3 +174,15 @@ Plot 21 is generated via an include directive:
 Plot 22 uses a different specific function in a file with plot commands:
 
 .. plot:: range6.py range10
+
+Plots 23 and 24 use output-base-name with a {counter}.
+
+.. plot::
+   :output-base-name: custom-base-name-{counter}
+
+   plt.plot(range(4))
+
+.. plot::
+   :output-base-name: custom-base-name-{counter}
+
+   plt.plot(range(6))