TST: Test for fix of type issue in empty groupby from DataFrame with categorical.

Author: louis

pandas/tests/reshape/test_concat.py

@@ -2747,14 +2747,18 @@ def test_concat_categorical_tz():
     tm.assert_series_equal(result, expected)
 
 
-def test_concat_categorical_unch():
+def test_concat_categorical_unchanged():
     # GH-12007
-    df1 = pd.DataFrame(pd.Series(["a", "b", "c"], dtype="category"))
-    s1 = pd.Series([0, 1, 2], index=[0, 1, 3])
-    df2 = pd.concat([df1, s1], axis=1)
-    result = df2.dtypes
-    expected = pd.Series(["category", "float64"], index=[0, 0])
-    tm.assert_series_equal(result, expected)
+    df = pd.DataFrame(pd.Series(["a", "b", "c"], dtype="category", name="A"))
+    ser = pd.Series([0, 1, 2], index=[0, 1, 3], name="B")
+    result = pd.concat([df, ser], axis=1)
+    expected = pd.DataFrame(
+        {
+            "A": pd.Series(["a", "b", "c", np.nan], dtype="category"),
+            "B": pd.Series([0, 1, np.nan, 2], dtype="float"),
+        }
+    )
+    tm.assert_equal(result, expected)
 
 
 def test_concat_datetimeindex_freq():