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

Author: Matias Heikkilä

pandas/tests/frame/test_sorting.py

@@ -227,6 +227,21 @@ def test_stable_descending_multicolumn_sort(self):
                                    kind='mergesort')
         assert_frame_equal(sorted_df, expected)
 
+    @pytest.mark.parametrize('seed', list(range(100)))
+    def test_sort_multi_index(self, seed):
+        # GH 25775
+        pd.np.random.seed(seed)
+        df1 = (pd.DataFrame(pd.np.random.rand(10, 5),
+                            columns=['a', 'b', 'c', 'd', 'e'])
+               .assign(b=lambda df: (df.b * 10).astype(int)))
+        df2 = df1.set_index(['a', 'b', 'c']).sort_index(
+            axis=0, level=['b', 'a'])
+        expected = pd.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({