Add test for __getitem__ syntax on str

Author: jtratner

pandas/tests/test_strings.py

@@ -1171,6 +1171,10 @@ def test_string_slice_get_syntax(self):
         expected = s.str.slice(stop=3)
         assert_series_equal(result, expected)
 
+        result = s.str[2::-1]
+        expected = s.str.slice(start=2, step=-1)
+        assert_series_equal(result, expected)
+
     def test_string_slice_out_of_bounds(self):
         s = Series([(1, 2), (1,), (3,4,5)])