def test_offset_by_time_invalid(self):
with self.assertRaises(_ud.UdunitsError) as cm:
_ud.offset_by_time(self.metre, -31622400.0)
ex = cm.exception
def test_offset_by_time_valid(self):
time_since = _ud.offset_by_time(self.second, -31622400.0)
self.assertIsNotNone(time_since)