def test_in_base_units(self):
#in_base_units() should return a new PhysicalQuantity instance
#using the base units, leaving the original instance intact
x = PhysicalQuantity(1, '1/h')
y = x.in_base_units()
self.assertEqual(y, PhysicalQuantity(1/3600.0, '1/s'))
self.assertEqual(x, PhysicalQuantity(1, '1/h'))
x = PhysicalQuantity(1, 'ft**-3')
y = x.in_base_units()
self.assertEqual(y, PhysicalQuantity(35.314666721488585, '1/m**3'))
x = PhysicalQuantity(1, 'ft**3')
y = x.in_base_units()
self.assertEqual(y, PhysicalQuantity(0.028316846592000004, 'm**3'))
x = PhysicalQuantity('5cm')
y = x.in_base_units()
self.assertEqual(y, PhysicalQuantity('0.05m'))
self.assertEqual(x, PhysicalQuantity('5cm'))
