def test_difference(self):
"Test difference (i.e. AND NOT) of two SimpleBitfields."
field = SimpleBitfield('110011')
field.difference(SimpleBitfield('001100'))
self.assertEqual(field._d, int('110011', 2))
field = SimpleBitfield('110011')
field.difference(SimpleBitfield('001110'))
self.assertEqual(field._d, int('110001', 2))
field = SimpleBitfield('110011')
field.difference(SimpleBitfield('011100'))
self.assertEqual(field._d, int('100011', 2))
