TST: adjust test

We no longer just hold onto the savefig kwargs passed in from the user so
adjust test to make sure the user values go through rather than simple
dictionary equality.

Set the rcparam to cover all of the lines added

Co-authored-by: Elliott Sales de Andrade <[email protected]>

Author: tacaswell

lib/matplotlib/tests/test_animation.py

@@ -70,6 +70,7 @@ def finish(self):
 
 def test_null_movie_writer(anim):
     # Test running an animation with NullMovieWriter.
+    plt.rcParams["savefig.facecolor"] = "auto"
     filename = "unused.null"
     dpi = 50
     savefig_kwargs = dict(foo=0)
@@ -82,7 +83,10 @@ def test_null_movie_writer(anim):
     assert writer.outfile == filename
     assert writer.dpi == dpi
     assert writer.args == ()
-    assert writer.savefig_kwargs == savefig_kwargs
+    # we enrich the savefig kwargs to ensure we composite transparent
+    # output to an opaque background
+    for k, v in savefig_kwargs.items():
+        assert writer.savefig_kwargs[k] == v
     assert writer._count == anim.save_count