public void CheckSumCalculation()
 {
     Calculator calculator = new Calculator(new Sum());
     int result = calculator.Calculate(10, 20);
     Assert.AreEqual(30, result);
 }
 public void CheckMinusCalculation()
 {
     Calculator calculator = new Calculator(new Minus());
     int result = calculator.Calculate(10, 20);
     Assert.AreEqual(-10, result);
 }