var factorial = function(n) {
    var result = 1;
    for(var i= 1 ; i<= n; i++){
        result= result *i;
     }
    return result;
};

println("The value of 5! should be " + 5*4*3*2*1);
println("The value of 5! is " + factorial(5));
println("The value of 0! should be 1");
println("The value of 0! is " + factorial(0));

Program.assertEqual(factorial(5), 120);
Program.assertEqual(factorial(0), 1);
Program.assertEqual(factorial(2), 2);
Program.assertEqual(factorial(4), 24);