Add a test for image-basename with multiple figures

Author: asmeurer

lib/matplotlib/tests/data/tinypages/some_plots.rst

@@ -180,7 +180,7 @@ Plot 22 uses a different specific function in a file with plot commands:
 
 .. plot:: range6.py range10
 
-Plots 23 and 24 use image-basename.
+Plots 23--25 use image-basename.
 
 .. plot::
    :image-basename: custom-basename-6
@@ -189,3 +189,12 @@ Plots 23 and 24 use image-basename.
 
 .. plot:: range4.py
    :image-basename: custom-basename-4
+
+.. plot::
+   :image-basename: custom-basename-4-6
+
+   plt.figure()
+   plt.plot(range(4))
+
+   plt.figure()
+   plt.plot(range(6))

lib/matplotlib/tests/test_sphinxext.py

@@ -92,9 +92,11 @@ 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 basename
+    # plots 23--25 use a custom basename
     assert filecmp.cmp(range_6, img_dir / 'custom-basename-6.png')
     assert filecmp.cmp(range_4, img_dir / 'custom-basename-4.png')
+    assert filecmp.cmp(range_4, img_dir / 'custom-basename-4-6_00.png')
+    assert filecmp.cmp(range_6, img_dir / 'custom-basename-4-6_01.png')
 
     # Modify the included plot
     contents = (tmp_path / 'included_plot_21.rst').read_bytes()