Add test for all-NA case

Author: snitish

pandas/tests/groupby/test_reductions.py

@@ -520,15 +520,27 @@ def test_sum_skipna_object(skipna):
         ("prod", [0, 1, 3, np.nan, 4, 5, 6, 7, -8, 9], "float64", "float64"),
         ("prod", [0, -1, 3, 4, 5, np.nan, 6, 7, 8, 9], "Float64", "Float64"),
         ("prod", [0, 1, 3, -4, 5, 6, 7, -8, np.nan, 9], "Int64", "Int64"),
+        ("prod", [np.nan] * 10, "float64", "float64"),
+        ("prod", [np.nan] * 10, "Float64", "Float64"),
+        ("prod", [np.nan] * 10, "Int64", "Int64"),
         ("var", [0, -1, 3, 4, np.nan, 5, 6, 7, 8, 9], "float64", "float64"),
         ("var", [0, 1, 3, -4, 5, 6, 7, -8, 9, np.nan], "Float64", "Float64"),
         ("var", [0, -1, 3, 4, 5, -6, 7, np.nan, 8, 9], "Int64", "Float64"),
+        ("var", [np.nan] * 10, "float64", "float64"),
+        ("var", [np.nan] * 10, "Float64", "Float64"),
+        ("var", [np.nan] * 10, "Int64", "Float64"),
         ("std", [0, 1, 3, -4, 5, 6, 7, -8, np.nan, 9], "float64", "float64"),
         ("std", [0, -1, 3, 4, 5, -6, 7, np.nan, 8, 9], "Float64", "Float64"),
         ("std", [0, 1, 3, -4, 5, 6, 7, -8, 9, np.nan], "Int64", "Float64"),
+        ("std", [np.nan] * 10, "float64", "float64"),
+        ("std", [np.nan] * 10, "Float64", "Float64"),
+        ("std", [np.nan] * 10, "Int64", "Float64"),
         ("sem", [0, -1, 3, 4, 5, -6, 7, np.nan, 8, 9], "float64", "float64"),
         ("sem", [0, 1, 3, -4, 5, 6, 7, -8, np.nan, 9], "Float64", "Float64"),
         ("sem", [0, -1, 3, 4, 5, -6, 7, 8, 9, np.nan], "Int64", "Float64"),
+        ("sem", [np.nan] * 10, "float64", "float64"),
+        ("sem", [np.nan] * 10, "Float64", "Float64"),
+        ("sem", [np.nan] * 10, "Int64", "Float64"),
         ("min", [0, -1, 3, 4, 5, -6, 7, np.nan, 8, 9], "float64", "float64"),
         ("min", [0, 1, 3, -4, 5, 6, 7, -8, np.nan, 9], "Float64", "Float64"),
         ("min", [0, -1, 3, 4, 5, -6, 7, 8, 9, np.nan], "Int64", "Int64"),
@@ -557,6 +569,9 @@ def test_sum_skipna_object(skipna):
             "datetime64[ns]",
             "datetime64[ns]",
         ),
+        ("min", [np.nan] * 10, "float64", "float64"),
+        ("min", [np.nan] * 10, "Float64", "Float64"),
+        ("min", [np.nan] * 10, "Int64", "Int64"),
         ("max", [0, -1, 3, 4, 5, -6, 7, np.nan, 8, 9], "float64", "float64"),
         ("max", [0, 1, 3, -4, 5, 6, 7, -8, np.nan, 9], "Float64", "Float64"),
         ("max", [0, -1, 3, 4, 5, -6, 7, 8, 9, np.nan], "Int64", "Int64"),
@@ -585,6 +600,9 @@ def test_sum_skipna_object(skipna):
             "datetime64[ns]",
             "datetime64[ns]",
         ),
+        ("max", [np.nan] * 10, "float64", "float64"),
+        ("max", [np.nan] * 10, "Float64", "Float64"),
+        ("max", [np.nan] * 10, "Int64", "Int64"),
         ("median", [0, -1, 3, 4, 5, -6, 7, np.nan, 8, 9], "float64", "float64"),
         ("median", [0, 1, 3, -4, 5, 6, 7, -8, np.nan, 9], "Float64", "Float64"),
         ("median", [0, -1, 3, 4, 5, -6, 7, 8, 9, np.nan], "Int64", "Float64"),
@@ -613,6 +631,9 @@ def test_sum_skipna_object(skipna):
             "datetime64[ns]",
             "datetime64[ns]",
         ),
+        ("median", [np.nan] * 10, "float64", "float64"),
+        ("median", [np.nan] * 10, "Float64", "Float64"),
+        ("median", [np.nan] * 10, "Int64", "Float64"),
     ],
 )
 def test_multifunc_skipna(func, values, dtype, result_dtype, skipna):