TST: Test sorting levels not aligned with index (#25775)

Author: Matias Heikkilä

pandas/tests/frame/test_sorting.py

@@ -11,6 +11,7 @@
 from pandas.tests.frame.common import TestData
 import pandas.util.testing as tm
 from pandas.util.testing import assert_frame_equal, assert_series_equal
+from io import StringIO
 
 
 class TestDataFrameSorting(TestData):
@@ -227,6 +228,30 @@ def test_stable_descending_multicolumn_sort(self):
                                    kind='mergesort')
         assert_frame_equal(sorted_df, expected)
 
+    def test_sort_multi_index(self):
+        # GH 25775
+        s = ',a,b,c,d,e' + \
+            '0,0.548,7,0.602,0.544,0.423' + \
+            '1,0.645,4,0.891,0.963,0.383' + \
+            '2,0.791,5,0.568,0.925,0.071' + \
+            '3,0.087,0,0.832,0.778,0.870' + \
+            '4,0.978,7,0.461,0.780,0.118' + \
+            '5,0.639,1,0.944,0.521,0.414' + \
+            '6,0.264,7,0.456,0.568,0.018' + \
+            '7,0.617,6,0.616,0.943,0.681' + \
+            '8,0.359,4,0.697,0.060,0.666' + \
+            '9,0.670,2,0.128,0.315,0.363'
+        data = StringIO(s)
+        df1 = (pd.read_csv(data)
+               .assign(b=lambda df: (df.b * 10).astype(int)))
+        df2 = df1.set_index(['a', 'b', 'c']).sort_index(
+            axis=0, level=['b', 'a'])
+        expected = DataFrame(df2.index.to_frame()[['a', 'b']].values,
+                             columns=['a', 'b']).assign(
+                                 b=lambda df: (df.b).astype(int))
+        result = df1.sort_values(by=['b', 'a']).reset_index()[['a', 'b']]
+        tm.assert_frame_equal(result, expected)
+
     def test_stable_categorial(self):
         # GH 16793
         df = DataFrame({