TST: Add Categorical Series test

Author: dsaxton

pandas/tests/arrays/categorical/test_analytics.py

@@ -90,10 +90,13 @@ def test_min_max_with_nan(self, skipna):
 
     @pytest.mark.parametrize("function", ["min", "max"])
     @pytest.mark.parametrize("skipna", [True, False])
-    def test_min_max_only_nan(self, function, skipna):
+    @pytest.mark.parametrize("box_in_series", [True, False])
+    def test_min_max_only_nan(self, function, skipna, box_in_series):
         # https://github.com/pandas-dev/pandas/issues/33450
-        cat = Categorical([np.nan], categories=[1, 2], ordered=True)
-        result = getattr(cat, function)(skipna=skipna)
+        arr = Categorical([np.nan], categories=[1, 2], ordered=True)
+        if box_in_series:
+            arr = Series(arr)
+        result = getattr(arr, function)(skipna=skipna)
         assert result is np.nan
 
     @pytest.mark.parametrize("method", ["min", "max"])