Add test for no-holidays calendar

Test for issue #31415

Author: David Hirschfeld

pandas/tests/tseries/holiday/test_calendar.py

@@ -98,3 +98,15 @@ class testCalendar(AbstractHolidayCalendar):
     Sat_before_Labor_Day_2031 = to_datetime("2031-08-30")
     next_working_day = Sat_before_Labor_Day_2031 + 0 * workDay
     assert next_working_day == to_datetime("2031-09-02")
+
+
+def test_no_holidays_calendar():
+    class NoHolidaysCalendar(AbstractHolidayCalendar):
+        pass
+
+    cal = NoHolidaysCalendar()
+    holidays = cal.holidays(
+        Timestamp("01-Jan-2020"),
+        Timestamp("01-Jan-2021")
+    )
+    assert holidays.empty