def test_constraints(self): def _constraint(value): if value != 5: return u'Value must be 5' param = Value(name='param') param._constraint = constraint(_constraint) self.assertFalse(param.isValid(4)) self.assertTrue(param.isValid(5)) model = Model([param]) param.value = 3 self.assertRaises(errors.ConstraintError, model.process)