Changes as requested in the review

Author: has2k1

doc/source/whatsnew/v0.25.2.rst

@@ -102,9 +102,6 @@ Other
 - Compatibility with Python 3.8 in :meth:`DataFrame.query` (:issue:`27261`)
 - Fix to ensure that tab-completion in an IPython console does not raise
   warnings for deprecated attributes (:issue:`27900`).
-- Bug in :meth:`Series.sort_values` when ``ascending`` is set to ``False`` and
-  ``kind`` is set to ``mergesort`` (:issue:`28697`)
-
 
 .. _whatsnew_0.252.contributors:
 

doc/source/whatsnew/v1.0.0.rst

@@ -301,6 +301,8 @@ Other
 - Using :meth:`DataFrame.replace` with overlapping keys in a nested dictionary will no longer raise, now matching the behavior of a flat dictionary (:issue:`27660`)
 - :meth:`DataFrame.to_csv` and :meth:`Series.to_csv` now support dicts as ``compression`` argument with key ``'method'`` being the compression method and others as additional compression options when the compression method is ``'zip'``. (:issue:`26023`)
 - :meth:`Series.append` will no longer raise a ``TypeError`` when passed a tuple of ``Series`` (:issue:`28410`)
+- Bug in :meth:`Series.sort_values` when ``ascending`` is set to ``False`` and
+  ``kind`` is set to ``mergesort`` (:issue:`28697`)
 
 .. _whatsnew_1000.contributors:
 

pandas/core/series.py

@@ -3079,9 +3079,7 @@ def sort_values(
             raise ValueError("ascending must be boolean")
 
         arr = self._values
-        indexer = nargsort(
-            arr, kind=kind, ascending=ascending, na_position=na_position
-        )
+        indexer = nargsort(arr, kind=kind, ascending=ascending, na_position=na_position)
 
         result = self._constructor(arr[indexer], index=self.index[indexer])
 

pandas/tests/series/test_sorting.py

@@ -86,8 +86,13 @@ def test_sort_values(self):
         with pytest.raises(ValueError, match=msg):
             s.sort_values(inplace=True)
 
-        # mergesort and ascending=False
+    def test_sort_values_mergesort(self):
         ser = Series([1, 2, 1, 3], ["first", "b", "second", "c"])
+        expected = Series([1, 1, 2, 3], ["first", "second", "b", "c"])
+        result = ser.sort_values(kind="mergesort")
+        tm.assert_series_equal(expected, result)
+
+        # ascending=False is not just a reverse of ascending=True
         expected = Series([3, 2, 1, 1], ["c", "b", "first", "second"])
         result = ser.sort_values(ascending=False, kind="mergesort")
         tm.assert_series_equal(expected, result)