Added test and whatsnew

Author: jhendricks487

doc/source/whatsnew/v3.0.0.rst

@@ -476,6 +476,7 @@ Other Removals
 - Disallow indexing an :class:`Index` with a boolean indexer of length zero, it now raises ``ValueError`` (:issue:`55820`)
 - Disallow non-standard (``np.ndarray``, :class:`Index`, :class:`ExtensionArray`, or :class:`Series`) to :func:`isin`, :func:`unique`, :func:`factorize` (:issue:`52986`)
 - Disallow passing a pandas type to :meth:`Index.view` (:issue:`55709`)
+- Disallow passing objects other than ``np.busdaycalendar`` to ``calendar`` parameter in :class:`CustomBusinessDay` (:issue:`60647`)
 - Disallow units other than "s", "ms", "us", "ns" for datetime64 and timedelta64 dtypes in :func:`array` (:issue:`53817`)
 - Removed "freq" keyword from :class:`PeriodArray` constructor, use "dtype" instead (:issue:`52462`)
 - Removed 'fastpath' keyword in :class:`Categorical` constructor (:issue:`20110`)

pandas/tests/tseries/offsets/test_custom_business_day.py

@@ -10,7 +10,11 @@
 import numpy as np
 import pytest
 
-from pandas._libs.tslibs.offsets import CDay
+from pandas._libs.tslibs.offsets import (
+    BDay,
+    CDay,
+    CustomBusinessDay,
+)
 
 from pandas import (
     _testing as tm,
@@ -97,3 +101,9 @@ def test_pickle_compat_0_14_1(self, datapath):
         cday0_14_1 = read_pickle(pth)
         cday = CDay(holidays=hdays)
         assert cday == cday0_14_1
+
+    def test_type_error_calendar(self):
+        bd = BDay(1)
+        msg = "Only np.busdaycalendar is supported for calendar"
+        with pytest.raises(TypeError, match=msg):
+            CustomBusinessDay(calendar=bd)