TST: Capture UserWarning for Bar plot with MultiIndex

Author: nrebena

pandas/tests/plotting/test_frame.py

@@ -3409,7 +3409,11 @@ def test_bar_multiindex(self):
         errors = gp3.std()
 
         # No assertion we just ensure that we can plot a MultiIndex bar plot
-        means.plot.bar(yerr=errors, capsize=4)
+        # and are getting a UserWarning
+        with pytest.warns(
+            UserWarning, match="Bar plot with a MultiIndex is not supported.",
+        ):
+            means.plot.bar(yerr=errors, capsize=4)
 
 
 def _generate_4_axes_via_gridspec():