Method _test_offset

pandas/tests/tseries/offsets/test_dst.py:91–155

(
        self, offset_name, offset_n, tstart, expected_utc_offset, performance_warning
    )

            )

    def _test_offset(
        self, offset_name, offset_n, tstart, expected_utc_offset, performance_warning
    ):
        offset = DateOffset(**{offset_name: offset_n})

        if (
            offset_name in ["hour", "minute", "second", "microsecond"]
            and offset_n == 1
            and tstart
            == Timestamp(
                "2013-11-03 01:59:59.999999-0500", tz=pytz.timezone("US/Eastern")
            )
        ):
            # This addition results in an ambiguous wall time
            err_msg = {
                "hour": "2013-11-03 01:59:59.999999",
                "minute": "2013-11-03 01:01:59.999999",
                "second": "2013-11-03 01:59:01.999999",
                "microsecond": "2013-11-03 01:59:59.000001",
            }[offset_name]
            with pytest.raises(ValueError, match=err_msg):
                tstart + offset
            # While we're here, let's check that we get the same behavior in a
            #  vectorized path
            dti = DatetimeIndex([tstart])
            warn_msg = "Non-vectorized DateOffset"
            with pytest.raises(ValueError, match=err_msg):
                with tm.assert_produces_warning(performance_warning, match=warn_msg):
                    dti + offset
            return

        t = tstart + offset
        if expected_utc_offset is not None:
            assert get_utc_offset_hours(t) == expected_utc_offset

        if offset_name == "weeks":
            # dates should match
            assert t.date() == timedelta(days=7 * offset.kwds["weeks"]) + tstart.date()
            # expect the same day of week, hour of day, minute, second, ...
            assert (
                t.dayofweek == tstart.dayofweek
                and t.hour == tstart.hour
                and t.minute == tstart.minute
                and t.second == tstart.second
            )
        elif offset_name == "days":
            # dates should match
            assert timedelta(offset.kwds["days"]) + tstart.date() == t.date()
            # expect the same hour of day, minute, second, ...
            assert (
                t.hour == tstart.hour
                and t.minute == tstart.minute
                and t.second == tstart.second
            )
        elif offset_name in self.valid_date_offsets_singular:
            # expect the singular offset value to match between tstart and t
            datepart_offset = getattr(
                t, offset_name if offset_name != "weekday" else "dayofweek"