static void Main(string[] args)
 {
     double x = 6.4;
     double y = 2.5;
     Console.WriteLine("x value is " + x);
     Console.WriteLine("y value is " +  y);
     Calcuator cal = new Calcuator();
     Console.WriteLine("Addition of x and y is "+cal.Addition(x, y));
     Console.WriteLine("Substraction of x and y is " + cal.Substraction(x, y));
     Console.WriteLine("Multiplication of x and y is " + cal.Multiplication(x, y));
     Console.WriteLine("Division of x and y is " + cal.Division(x, y));
     Console.WriteLine("Modulos  of x and y is " + cal.Modulos(x, y));
 }
        public void TestSubstraction()
        {
            Calcuator calc = new Calcuator();

            // arrange
            double x = 6.4;
            double y = 4.2;
            double expected = 2.2;

            // act
            double result = calc.Substraction(x, y);

            // assert

            Assert.AreEqual(expected,result);
        }