TST: add test for indexing with single/double tuples (pandas-dev#29448)

Author: ganevgv

pandas/tests/frame/indexing/test_indexing.py

@@ -2624,6 +2624,17 @@ def test_index_namedtuple(self):
         result = df.loc[IndexType("foo", "bar")]["A"]
         assert result == 1
 
+    @pytest.mark.parametrize("tpl", [tuple([1]), tuple([1, 2])])
+    def test_index_single_double_tuples(self, tpl):
+        # GH 20991
+        idx = pd.Index([tuple([1]), tuple([1, 2])], name="A", tupleize_cols=False)
+        df = DataFrame(index=idx)
+
+        result = df.loc[[tpl]]
+        idx = pd.Index([tpl], name="A", tupleize_cols=False)
+        expected = DataFrame(index=idx)
+        tm.assert_frame_equal(result, expected)
+
     def test_boolean_indexing(self):
         idx = list(range(3))
         cols = ["A", "B", "C"]