Testing and Debugging - JavaScript: Novice to Ninja - page 340

for (var i=1 , max = Math.sqrt(n); i <= max ; i++) {
if (n%i === 0){
factors.push(i,n/i);
}
}
return factors.sort(function(a,b){ return a > b; });
}
We'll also sort the array at the end using the sort() method with a callback we saw in
Chapter 4 .
Refresh SpecRunner.html to confirm that the tests still pass.
Now that our tests are passing and our code has been refactored, it's time to add some more
functionality. Let's write another function called isPrime() that will return true if a
number is prime and false if it isn't. Let's start by writing the test by adding the follow-
ing code to the numberSpec.js file:
spec/numberSpec.js (incomplete)
describe("The isPrime() function", function() {
it("should say 2 is prime", function() {
expect(isPrime(2)).toBe(true);
});
it("should say 10 is not prime", function() {
expect(isPrime(10)).not.toBe(true);
});
});
We're using a new describe block because we are testing a different function. This
block has two specs―one to check whether true is returned when a prime number ( 2 )
is provided as an argument and another to check that true is not returned if a non-prime
number ( 10 ) is given as an argument. These specs use the toBe() matcher, which allows
you to check if something is true or false . Note the nice use of negation using the not