TST: Add test for groupby aggregatation with nested dictionary (#50079)

Co-authored-by: Lakmal Pinnaduwage <[email protected]>

Author: talukder-sowrov

pandas/tests/groupby/aggregate/test_aggregate.py

@@ -468,6 +468,16 @@ def test_groupby_agg_coercing_bools():
     tm.assert_series_equal(result, expected)
 
 
+def test_groupby_agg_dict_with_getitem():
+    # issue 25471
+    dat = DataFrame({"A": ["A", "A", "B", "B", "B"], "B": [1, 2, 1, 1, 2]})
+    result = dat.groupby("A")[["B"]].agg({"B": "sum"})
+
+    expected = DataFrame({"B": [3, 4]}, index=["A", "B"]).rename_axis("A", axis=0)
+
+    tm.assert_frame_equal(result, expected)
+
+
 @pytest.mark.parametrize(
     "op",
     [