TST: tests for bug Index.str.split(expand=True) not nan-safe (pandas-dev#23677)

Author: meiermark

doc/source/whatsnew/v0.24.0.rst

@@ -1261,7 +1261,7 @@ Numeric
 Strings
 ^^^^^^^
 
-- BUG in :func:`Index.str.partition` is not nan-safe (:issue:`23558`)
+- BUG in :meth:`Index.str.partition` was not nan-safe (:issue:`23558`).
 -
 -
 

pandas/tests/test_strings.py

@@ -2330,24 +2330,33 @@ def test_split_to_dataframe(self):
             s.str.split('_', expand="not_a_boolean")
 
     def test_split_to_multiindex_expand(self):
-        idx = Index(['nosplit', 'alsonosplit'])
+        idx = Index(['nosplit', 'alsonosplit', np.nan])
         result = idx.str.split('_', expand=True)
         exp = idx
         tm.assert_index_equal(result, exp)
         assert result.nlevels == 1
 
-        idx = Index(['some_equal_splits', 'with_no_nans'])
+        idx = Index(['some_equal_splits', 'with_no_nans', np.nan, None])
         result = idx.str.split('_', expand=True)
-        exp = MultiIndex.from_tuples([('some', 'equal', 'splits'), (
-            'with', 'no', 'nans')])
+        exp = MultiIndex.from_tuples([('some', 'equal', 'splits'),
+                                      ('with', 'no', 'nans'),
+                                      [np.nan, np.nan, np.nan],
+                                      [None, None, None]])
         tm.assert_index_equal(result, exp)
         assert result.nlevels == 3
 
-        idx = Index(['some_unequal_splits', 'one_of_these_things_is_not'])
+        idx = Index(['some_unequal_splits',
+                     'one_of_these_things_is_not',
+                     np.nan, None])
         result = idx.str.split('_', expand=True)
-        exp = MultiIndex.from_tuples([('some', 'unequal', 'splits', NA, NA, NA
-                                       ), ('one', 'of', 'these', 'things',
-                                           'is', 'not')])
+        exp = MultiIndex.from_tuples([('some', 'unequal', 'splits',
+                                       NA, NA, NA),
+                                      ('one', 'of', 'these',
+                                       'things', 'is', 'not'),
+                                      (np.nan, np.nan, np.nan,
+                                       np.nan, np.nan, np.nan),
+                                      (None, None, None,
+                                       None, None, None)])
         tm.assert_index_equal(result, exp)
         assert result.nlevels == 6
 
@@ -2480,12 +2489,12 @@ def test_partition_series(self):
         # Not split
         values = Series(['abc', 'cde', NA, 'fgh', None])
         result = values.str.partition('_', expand=False)
-        exp = Series([('abc', '', ''), ('cde', '', ''), NA, 
+        exp = Series([('abc', '', ''), ('cde', '', ''), NA,
                       ('fgh', '', ''), None])
         tm.assert_series_equal(result, exp)
 
         result = values.str.rpartition('_', expand=False)
-        exp = Series([('', '', 'abc'), ('', '', 'cde'), NA, 
+        exp = Series([('', '', 'abc'), ('', '', 'cde'), NA,
                       ('', '', 'fgh'), None])
         tm.assert_series_equal(result, exp)