TST: Refactor test for empty groupby with categorical data.

Author: louis

pandas/tests/groupby/test_categorical.py

@@ -781,6 +781,18 @@ def test_categorical_no_compress():
     tm.assert_numpy_array_equal(result, exp)
 
 
+def test_groupby_empty_with_category():
+    # GH-9614
+    df = pd.DataFrame({"A": [None] * 3, "B": pd.Categorical(["train", "train", "test"])})
+    result = df.groupby("A").first()["B"]
+    expected = pd.Series(
+        pd.Categorical([], categories=["test", "train"]),
+        index=pd.Series([], dtype="object", name="A"),
+        name="B",
+    )
+    tm.assert_series_equal(result, expected)
+
+
 def test_sort():
 
     # http://stackoverflow.com/questions/23814368/sorting-pandas-

pandas/tests/groupby/test_groupby.py

@@ -1825,18 +1825,6 @@ def test_groupby_empty_list_raises():
         df.groupby([[]])
 
 
-def test_groupby_with_empty_category():
-    # GH-9614
-    df = pd.DataFrame({"id": [None] * 3, "spam": [None] * 3})
-    df["spam"] = df["spam"].astype("category")
-    df["spam"] == "spam"  # works as expected
-    result = df.groupby("id").first()["spam"] == "spam"
-    expected = Series(
-        [], name="spam", dtype=bool, index=pd.Series([], dtype="object", name="id")
-    )
-    tm.assert_series_equal(result, expected)
-
-
 def test_groupby_multiindex_series_keys_len_equal_group_axis():
     # GH 25704
     index_array = [["x", "x"], ["a", "b"], ["k", "k"]]