diff --git a/pandas/tests/groupby/aggregate/test_other.py b/pandas/tests/groupby/aggregate/test_other.py index 606539a564323..61db4cee1ab02 100644 --- a/pandas/tests/groupby/aggregate/test_other.py +++ b/pandas/tests/groupby/aggregate/test_other.py @@ -512,3 +512,14 @@ def test_agg_category_nansum(observed): if observed: expected = expected[expected != 0] tm.assert_series_equal(result, expected) + + +def test_agg_list_like_func(): + # GH 18473 + df = pd.DataFrame({'A': [str(x) for x in range(3)], + 'B': [str(x) for x in range(3)]}) + grouped = df.groupby('A', as_index=False, sort=False) + result = grouped.agg({'B': lambda x: list(x)}) + expected = pd.DataFrame({'A': [str(x) for x in range(3)], + 'B': [[str(x)] for x in range(3)]}) + tm.assert_frame_equal(result, expected)