diff --git a/pandas/tests/groupby/test_function.py b/pandas/tests/groupby/test_function.py index 6f19ec40c2520..e693962e57ac3 100644 --- a/pandas/tests/groupby/test_function.py +++ b/pandas/tests/groupby/test_function.py @@ -85,6 +85,24 @@ def test_max_min_non_numeric(): assert "ss" in result +def test_min_date_with_nans(): + # GH26321 + dates = pd.to_datetime( + pd.Series(["2019-05-09", "2019-05-09", "2019-05-09"]), format="%Y-%m-%d" + ).dt.date + df = pd.DataFrame({"a": [np.nan, "1", np.nan], "b": [0, 1, 1], "c": dates}) + + result = df.groupby("b", as_index=False)["c"].min()["c"] + expected = pd.to_datetime( + pd.Series(["2019-05-09", "2019-05-09"], name="c"), format="%Y-%m-%d" + ).dt.date + tm.assert_series_equal(result, expected) + + result = df.groupby("b")["c"].min() + expected.index.name = "b" + tm.assert_series_equal(result, expected) + + def test_intercept_builtin_sum(): s = Series([1.0, 2.0, np.nan, 3.0]) grouped = s.groupby([0, 1, 2, 2])