def test_cfunits_conform(self):
units_kelvin = get_units_object('kelvin')
# Conversion of celsius units to kelvin.
attrs = {k: 1 for k in NETCDF_ATTRIBUTES_TO_REMOVE_ON_VALUE_CHANGE}
var = Variable(name='tas', units='celsius', value=self.value, attrs=attrs)
self.assertEqual(len(var.attrs), 4)
var.cfunits_conform(units_kelvin)
self.assertNumpyAll(var.value, np.ma.array([278.15] * 3))
self.assertEqual(var.cfunits, units_kelvin)
self.assertEqual(var.units, 'kelvin')
self.assertEqual(len(var.attrs), 0)
# If there are no units associated with a variable, conforming the units should fail.
var = Variable(name='tas', units=None, value=self.value)
with self.assertRaises(NoUnitsError):
var.cfunits_conform(units_kelvin)
# Conversion should fail for nonequivalent units.
var = Variable(name='tas', units='kelvin', value=self.value)
with self.assertRaises(ValueError):
var.cfunits_conform(get_units_object('grams'))
# The data type should always be updated to match the output from CF units backend.
av = Variable(value=np.array([4, 5, 6]), dtype=int)
self.assertEqual(av.dtype, np.dtype(int))
with self.assertRaises(NoUnitsError):
av.cfunits_conform('K')
av.units = 'celsius'
av.cfunits_conform('K')
self.assertIsNone(av._dtype)
self.assertEqual(av.dtype, av.value.dtype)
