Method test_system_transitions

Lib/test/datetimetester.py:6909–6946

(self)

        hasattr(_time, "tzset"), "time module has no attribute tzset"
    )
    def test_system_transitions(self):
        if ('Riyadh8' in self.zonename or
            # From tzdata NEWS file:
            # The files solar87, solar88, and solar89 are no longer distributed.
            # They were a negative experiment - that is, a demonstration that
            # tz data can represent solar time only with some difficulty and error.
            # Their presence in the distribution caused confusion, as Riyadh
            # civil time was generally not solar time in those years.
                self.zonename.startswith('right/')):
            self.skipTest("Skipping %s" % self.zonename)
        tz = self.tz
        with self._change_tz(self.zonename):
            for udt, shift in tz.transitions():
                if udt.year >= 2037:
                    # System support for times around the end of 32-bit time_t
                    # and later is flaky on many systems.
                    break
                s0 = (udt - datetime(1970, 1, 1)) // SEC
                ss = shift // SEC   # shift seconds
                for x in [-40 * 3600, -20 * 3600, -1, 0,
                          ss - 1, ss + 20 * 3600, ss + 40 * 3600]:
                    s = s0 + x
                    sdt = datetime.fromtimestamp(s)
                    tzdt = datetime.fromtimestamp(s, tz).replace(tzinfo=None)
                    self.assertEquivDatetimes(sdt, tzdt)
                    s1 = sdt.timestamp()
                    self.assertEqual(s, s1)
                if ss > 0:  # gap
                    # Create local time inside the gap
                    dt = datetime.fromtimestamp(s0) - shift / 2
                    ts0 = dt.timestamp()
                    ts1 = dt.replace(fold=1).timestamp()
                    self.assertEqual(ts0, s0 + ss / 2)
                    self.assertEqual(ts1, s0 - ss / 2)
                    # gh-83861
                    utc0 = dt.astimezone(timezone.utc)
                    utc1 = dt.replace(fold=1).astimezone(timezone.utc)
                    self.assertEqual(utc0, utc1 + timedelta(0, ss))


class ZoneInfoCompleteTest(unittest.TestSuite):