diff --git a/xarray/tests/test_groupby.py b/xarray/tests/test_groupby.py
index 371e5e0f7af..2985b38258d 100644
--- a/xarray/tests/test_groupby.py
+++ b/xarray/tests/test_groupby.py
@@ -559,3 +559,4 @@ def test_groupby_get_group(dataset):
 # TODO: move other groupby tests from test_dataset and test_dataarray over here
 # TODO: add tests for groupby.__getitem__
 # TODO: add tests for groupby.get_group
+# TODO: add tests for fg.map with GroupBy