test_num2date_precision failure on various architectures

[sebastic]

The Debian package build failed on various architectures due to test failures:

=================================== FAILURES ===================================
___________________________ test_num2date_precision ____________________________

    def test_num2date_precision():
        if sys.platform.startswith("win"):
            pytest.skip("skipping tests that require float128 on windows")
        testdates = [(1271, 3, 18, 19, 41, 33),
                     (1271, 3, 18, 19, 41, 32, 999998)]
        unitinc = ['microseconds', 'seconds', 'minutes', 'hours', 'days']
        for cc in ['standard', 'gregorian', 'julian', 'proleptic_gregorian',
                   'noleap', 'all_leap', '365_day', '366_day', '360_day']:
            for uinc in unitinc:
                if cc in ['standard', 'gregorian', 'julian']:
                    units = uinc + ' since -4713-01-01 12:00:00'
                elif cc in ['proleptic_gregorian']:
                    units = uinc + ' since -4714-01-01 12:00:00'
                elif cc in ['noleap', 'all_leap', '365_day', '366_day', '360_day']:
                    units = uinc + ' since 0000-01-01 12:00:00'
                # scalar
                date = datetimex(*testdates[0], calendar=cc)
                num = date2num(date, units, calendar=cc, longdouble=True)
                date2 = num2date(num, units, calendar=cc)
                assert date == date2
                # array
                date = [ datetimex(*dd, calendar=cc) for dd in testdates ]
                num = date2num(date, units, calendar=cc, longdouble=True)
                date2 = num2date(num, units, calendar=cc)
                for i in range(len(date)):
>                   assert date[i] == date2[i]
E                   AssertionError: assert cftime.datetime(1271, 3, 18, 19, 41, 32, 999998, calendar='standard', has_year_zero=False) == cftime.DatetimeGregorian(1271, 3, 18, 19, 41, 33, 0, has_year_zero=False)

test/test_cftime.py:2210: AssertionError
=============================== warnings summary ===============================
.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py::test_string_format2
  /<<PKGBUILDDIR>>/.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py:1694: CFWarning: this date/calendar/year zero convention is not supported by CF
    dt = cftime.datetime(-4713, 1, 1, 12, 0, 0, 10)

.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py::test_string_format2
  /<<PKGBUILDDIR>>/.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py:1701: CFWarning: this date/calendar/year zero convention is not supported by CF
    dt = cftime.datetime(-713, 1, 1, 12, 0, 0, 10)

.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py::test_strptime
  /<<PKGBUILDDIR>>/.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py:1717: CFWarning: this date/calendar/year zero convention is not supported by CF
    d = cftime.datetime.strptime('24/Aug/-4712:17:57:26', '%d/%b/%Y:%H:%M:%S',calendar='julian')

.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py::test_strptime
  /<<PKGBUILDDIR>>/.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py:1719: CFWarning: this date/calendar/year zero convention is not supported by CF
    d = cftime.datetime.strptime('24/August/-4712:17:57:26', '%d/%B/%Y:%H:%M:%S',calendar='julian')

.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py::test_strptime
  /<<PKGBUILDDIR>>/.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py:1721: CFWarning: this date/calendar/year zero convention is not supported by CF
    d = cftime.datetime.strptime("-4712", "%Y", calendar="julian")

.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py::test_string_isoformat
  /<<PKGBUILDDIR>>/.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py:1733: CFWarning: this date/calendar/year zero convention is not supported by CF
    dt = cftime.datetime(-4713, 1, 1, 12, 0, 0, 10)

.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py::test_string_isoformat
  /<<PKGBUILDDIR>>/.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py:1738: CFWarning: this date/calendar/year zero convention is not supported by CF
    dt = cftime.datetime(-713, 1, 1, 12, 0, 0, 10)

.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py::test_num2date_precision
  /<<PKGBUILDDIR>>/.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py:2202: CFWarning: this date/calendar/year zero convention is not supported by CF
    num = date2num(date, units, calendar=cc, longdouble=True)

.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py::test_num2date_precision
  /<<PKGBUILDDIR>>/.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py:2203: CFWarning: this date/calendar/year zero convention is not supported by CF
    date2 = num2date(num, units, calendar=cc)

.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py::test_num2date_precision
  /<<PKGBUILDDIR>>/.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py:2207: CFWarning: this date/calendar/year zero convention is not supported by CF
    num = date2num(date, units, calendar=cc, longdouble=True)

.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py::test_num2date_precision
  /<<PKGBUILDDIR>>/.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py:2208: CFWarning: this date/calendar/year zero convention is not supported by CF
    date2 = num2date(num, units, calendar=cc)

.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py::test_num2date_precision
  /<<PKGBUILDDIR>>/.pybuild/cpython3_3.10_cftime/build/test/test_cftime.py:2213: CFWarning: this date/calendar/year zero convention is not supported by CF
    date2 = num2date(num, units, calendar=cc)

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html

---------- coverage: platform linux, python 3.10.7-final-0 -----------
Name                  Stmts   Miss  Cover   Missing
---------------------------------------------------
cftime/__init__.py        5      0   100%
cftime/_strptime.py      99     21    79%   53, 96-97, 102, 109-123, 127, 130, 138-142
---------------------------------------------------
TOTAL                   104     21    80%

=========================== short test summary info ============================
FAILED test/test_cftime.py::test_num2date_precision - AssertionError: assert ...
============ 1 failed, 2271 passed, 12 warnings in 82.00s (0:01:21) ============

Full buildlogs: armel, armhf, mipsel, hppa

[jswhit]

This test relies on numpy's longdouble type actually being extended precision. It is not on windows, which is why the test is skipped there. Apparently it's not extended precision on armel, armhf, mipsel or hppa either. The solution is probably to check using numpy.finfo and skip the test if a numpy.longdouble doesn't have any more precision than numpy.float.

[jswhit]

PR #294 should fix those failing tests (by skipping them on platforms where numpy.longdouble doesn't have sufficient precision)

[sebastic]

Confirmed fixed with the changes from #294 on armhf.