Test for all join_type values

Author: Dr-Irv

pandas/tests/reshape/merge/test_join.py

@@ -727,6 +727,31 @@ def test_panel_join_many(self):
             pytest.raises(ValueError, panels[0].join, panels[1:],
                           how='right')
 
+    def test_join_multi_to_multi(self, join_type):
+        # GH 20475
+        leftindex = MultiIndex.from_product([list('abc'), list('xy'), [1, 2]],
+                                            names=['abc', 'xy', 'num'])
+        left = DataFrame({'v1': range(12)}, index=leftindex)
+
+        rightindex = MultiIndex.from_product([list('abc'), list('xy')],
+                                             names=['abc', 'xy'])
+        right = DataFrame({'v2': [100 * i for i in range(1, 7)]},
+                          index=rightindex)
+
+        result = left.join(right, on=['abc', 'xy'], how=join_type)
+        expected = (left.reset_index()
+                        .merge(right.reset_index(),
+                               on=['abc', 'xy'], how=join_type)
+                        .set_index(['abc', 'xy', 'num'])
+                    )
+        assert_frame_equal(expected, result)
+
+        with pytest.raises(ValueError):
+            left.join(right, on='xy', how=join_type)
+
+        with pytest.raises(ValueError):
+            right.join(left, on=['abc', 'xy'], how=join_type)
+
 
 def _check_join(left, right, result, join_col, how='left',
                 lsuffix='_x', rsuffix='_y'):

pandas/tests/test_join.py

@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 
 import numpy as np
-from pandas import Index, DataFrame, Categorical, merge, MultiIndex
+from pandas import Index, DataFrame, Categorical, merge
 
 from pandas._libs import join as _join
 import pandas.util.testing as tm
@@ -233,22 +233,3 @@ def test_merge_join_categorical_multiindex():
     result = a.join(b, on=['Cat1', 'Int1'])
     expected = expected.drop(['Cat', 'Int'], axis=1)
     assert_frame_equal(expected, result)
-
-
-def test_join_multi_to_multi():
-    leftindex = MultiIndex.from_product([list('abc'), list('xy'), [1, 2]],
-                                        names=['abc', 'xy', 'num'])
-    left = DataFrame({'v1': range(12)}, index=leftindex)
-
-    rightindex = MultiIndex.from_product([list('abc'), list('xy')],
-                                         names=['abc', 'xy'])
-    right = DataFrame({'v2': [100 * i for i in range(1, 7)]},
-                      index=rightindex)
-
-    result = left.join(right, on=['abc', 'xy'], how='inner')
-    expected = (left.reset_index()
-                    .merge(right.reset_index(),
-                           on=['abc', 'xy'], how='inner')
-                    .set_index(['abc', 'xy', 'num'])
-                )
-    assert_frame_equal(expected, result)