def test_1_should_Plus(self):
     operator = Operator(1)
     self.assertEqual('+' , operator.toString())
 def test_2_should_Sub(self):
     operator = Operator(2)
     self.assertEqual('-' , operator.toString())
 def test_3_should_Mul(self):
     operator = Operator(3)
     self.assertEqual('*' , operator.toString())