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#!/usr/bin/python3
# Author: Benjamin Drung <bdrung@ubuntu.com>
"""Test timezones using Python's zoneinfo module."""
import datetime
import os
import pathlib
import re
import sys
import typing
import unittest
import zoneinfo
ROOT_DIR = pathlib.Path(__file__).parent.parent.parent
def read_backwards_links(backwards_file: pathlib.Path) -> dict[str, str]:
"""Read backwards compatibility links from the upstream backwards file."""
backwards_links = {}
for line in backwards_file.read_text(encoding="utf-8").splitlines():
match = re.match(r"^Link\t(?P<target>\S+)\t+(?P<link_name>\S+)", line)
if not match:
continue
backwards_links[match.group("link_name")] = match.group("target")
return backwards_links
class TestZoneinfo(unittest.TestCase):
"""Test timezones using Python's zoneinfo module."""
def _hours(self, delta: typing.Optional[datetime.timedelta]) -> int:
assert delta is not None
total_seconds = int(delta.total_seconds())
self.assertEqual(total_seconds % 3600, 0)
return total_seconds // 3600
def test_available_timezones_count(self) -> None:
"""Test available_timezones() count to be reasonable."""
zones = len(zoneinfo.available_timezones())
self.assertGreaterEqual(zones, 597, "less zones than 2022g-2")
self.assertLess(zones, round(597 * 1.1), ">10% more zones than 2022g-2")
def test_daylight_saving_transition(self) -> None:
"""Test daylight saving time transition from Python documentation."""
tzinfo = zoneinfo.ZoneInfo("America/Los_Angeles")
date = datetime.datetime(2020, 10, 31, 12, tzinfo=tzinfo)
self.assertEqual(date.tzname(), "PDT")
next_day = date + datetime.timedelta(days=1)
self.assertEqual(next_day.tzname(), "PST")
def _assert_equal_zones_at_date(
self,
date: datetime.datetime,
timezone1: zoneinfo.ZoneInfo,
timezone2: zoneinfo.ZoneInfo,
) -> None:
date1 = date.replace(tzinfo=timezone1)
date2 = date.replace(tzinfo=timezone2)
self.assertEqual(date1 - date2, datetime.timedelta(seconds=0))
self.assertEqual(date1.tzname(), date2.tzname())
def _assert_equal_zones(
self, timezone1: zoneinfo.ZoneInfo, timezone2: zoneinfo.ZoneInfo
) -> None:
"""Test timezones to be heuristically equal regardless of the name."""
october_2020 = datetime.datetime(2020, 10, 31, 12)
self._assert_equal_zones_at_date(october_2020, timezone1, timezone2)
july_2021 = datetime.datetime(2021, 7, 3, 12)
self._assert_equal_zones_at_date(july_2021, timezone1, timezone2)
@unittest.skipIf(os.environ.get("PYTHONTZPATH"), "requires installed tzdata")
def test_localtime(self) -> None:
"""Test 'localtime' timezone."""
localtime = pathlib.Path("/etc/localtime")
zone = str(localtime.resolve().relative_to("/usr/share/zoneinfo"))
tzinfo = zoneinfo.ZoneInfo("localtime")
self._assert_equal_zones(tzinfo, zoneinfo.ZoneInfo(zone))
def _test_timezone(self, zone: str) -> None:
"""Test zone to load, have a name, and have a reasonable offset."""
tzinfo = zoneinfo.ZoneInfo(zone)
self.assertEqual(str(tzinfo), zone)
date = datetime.datetime(2020, 10, 31, 12, tzinfo=tzinfo)
tzname = date.tzname()
assert tzname is not None
self.assertGreaterEqual(len(tzname), 3, tzname)
self.assertLessEqual(len(tzname), 5, tzname)
utc_offset = date.utcoffset()
assert utc_offset is not None
self.assertEqual(int(utc_offset.total_seconds()) % 900, 0)
self.assertLessEqual(utc_offset, datetime.timedelta(hours=14))
def test_pre_1970_timestamps(self) -> None:
"""Test pre-1970 timestamps of Berlin and Oslo being different."""
berlin = zoneinfo.ZoneInfo("Europe/Berlin")
date = datetime.datetime(1960, 7, 1, tzinfo=berlin)
self.assertEqual(self._hours(date.utcoffset()), 1)
oslo = zoneinfo.ZoneInfo("Europe/Oslo")
self.assertEqual(self._hours(date.replace(tzinfo=oslo).utcoffset()), 2)
def test_post_1970_symlinks_consistency(self) -> None:
"""Test that post-1970 symlinks are consistent with pre-1970 timezones.
Building tzdata with PACKRATDATA=backzone will result in separate
time zones for time zones that differ only before 1970. These time
zones should behave identical after 1970. Building tzdata without
PACKRATDATA=backzone will result in one of the time zones become a
symlink to the other time zone.
"""
links = read_backwards_links(ROOT_DIR / "backward")
for link_name, target in links.items():
with self.subTest(f"{link_name} -> {target}"):
tz_link = zoneinfo.ZoneInfo(link_name)
tz_target = zoneinfo.ZoneInfo(target)
now = datetime.datetime.now()
self._assert_equal_zones_at_date(now, tz_link, tz_target)
future = now + datetime.timedelta(days=30 * 6)
self._assert_equal_zones_at_date(future, tz_link, tz_target)
def test_timezones(self) -> None:
"""Test all zones to load, have a name, and have a reasonable offset."""
for zone in zoneinfo.available_timezones():
with self.subTest(zone=zone):
self._test_timezone(zone)
def test_2022g(self) -> None:
"""Test new zone America/Ciudad_Juarez from 2022g release."""
tzinfo = zoneinfo.ZoneInfo("America/Ciudad_Juarez")
date = datetime.datetime(2022, 12, 1, tzinfo=tzinfo)
self.assertEqual(self._hours(date.utcoffset()), -7)
def test_2023a(self) -> None:
"""Test Egypt uses DST again from 2023a release."""
tzinfo = zoneinfo.ZoneInfo("Africa/Cairo")
date = datetime.datetime(2023, 4, 28, 12, 0, tzinfo=tzinfo)
self.assertEqual(self._hours(date.utcoffset()), 3)
def test_2023c(self) -> None:
"""Test Lebanon's reverted DST delay from 2023c release."""
tzinfo = zoneinfo.ZoneInfo("Asia/Beirut")
date = datetime.datetime(2023, 4, 2, tzinfo=tzinfo)
self.assertEqual(self._hours(date.utcoffset()), 3)
def main() -> None:
"""Run unit tests in verbose mode."""
argv = sys.argv.copy()
argv.insert(1, "-v")
unittest.main(argv=argv)
if __name__ == "__main__":
main()
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