TST:Same return values in drop_duplicates for Series and DataFrames(#14192)

Add keep kwarg and new columns

Author: mroeschke

pandas/tests/test_base.py

@@ -949,6 +949,21 @@ def test_duplicated_drop_duplicates_index(self):
                 s.drop_duplicates(inplace=True)
                 tm.assert_series_equal(s, original)
 
+    def test_drop_duplicates_series_vs_dataframe(self):
+        # GH 14192
+        df = pd.DataFrame({'a': [1, 1, 1, 'one', 'one'],
+                           'b': [2, 2, np.nan, np.nan, np.nan],
+                           'c': [3, 3, np.nan, np.nan, 'three'],
+                           'd': [1, 2, 3, 4, 4],
+                           'e': [datetime(2015, 1, 1), datetime(2015, 1, 1),
+                                 datetime(2015, 2, 1), pd.NaT, pd.NaT]
+                           })
+        for column in df.columns:
+            for keep in ['first', 'last', False]:
+                dropped_frame = df[[column]].drop_duplicates(keep=keep)
+                dropped_series = df[column].drop_duplicates(keep=keep)
+                tm.assert_frame_equal(dropped_frame, dropped_series.to_frame())
+
     def test_fillna(self):
         # # GH 11343
         # though Index.fillna and Series.fillna has separate impl,