Update whatsnew entry; fix tests

Author: sahildua2305

doc/source/whatsnew/v0.19.0.txt

@@ -332,6 +332,7 @@ API changes
 - ``PeriodIndex.fillna`` with ``Period`` has different freq now coerces to ``object`` dtype (:issue:`13664`)
 - More informative exceptions are passed through the csv parser. The exception type would now be the original exception type instead of ``CParserError``. (:issue:`13652`)
 - ``astype()`` will now accept a dict of column name to data types mapping as the ``dtype`` argument. (:issue:`12086`)
+- `Series.sort_index`` will now accept kwargs ``kind`` and ``na_position`` (:issue:`13589`)
 
 
 .. _whatsnew_0190.api.tolist:
@@ -731,5 +732,3 @@ Bug Fixes
 - Bug where ``pd.read_gbq()`` could throw ``ImportError: No module named discovery`` as a result of a naming conflict with another python package called apiclient  (:issue:`13454`)
 - Bug in ``Index.union`` returns an incorrect result with a named empty index (:issue:`13432`)
 - Bugs in ``Index.difference`` and ``DataFrame.join`` raise in Python3 when using mixed-integer indexes (:issue:`13432`, :issue:`12814`)
-
-- Bug in ``Series.sort_index`` didn't accept kwargs ``kind`` and ``na_position`` (:issue:`13589`)

pandas/tests/series/test_sorting.py

@@ -151,11 +151,11 @@ def test_sort_index_nan(self):
         ser = Series(['A', np.nan, 'C', 'D'], [1, 2, 0, np.nan])
 
         # na_position='last', kind='quicksort'
-        sorted_series = ser.sort_index(kind='quicksort', na_position='last')
-        expected_series = Series(['C', 'A', np.nan, 'D'], [0, 1, 2, np.nan])
-        assert_series_equal(sorted_series, expected_series)
+        result = ser.sort_index(kind='quicksort', na_position='last')
+        expected = Series(['C', 'A', np.nan, 'D'], [0, 1, 2, np.nan])
+        assert_series_equal(result, expected)
 
         # na_position='first'
-        sorted = ser.sort_index(na_position='first')
+        result = ser.sort_index(na_position='first')
         expected = Series(['D', 'C', 'A', np.nan], [np.nan, 0, 1, 2])
-        assert_series_equal(sorted, expected)
+        assert_series_equal(result, expected)