Additional test case for Arguments Optional

Hello CodeCampers!

Tell us what’s happening:
In the challenge linked below, it is asked “If either argument isn’t a valid number, return undefined.”
Please, consider adding a test where the first argument isn’t a valid number, but the second is.

I passed the challenge with this code:

//buggy function
function addTogether(...args) {

  if (arguments.length == 1 && typeof(args[0]) == 'number')
  return ( val => (typeof(val) === 'number') ? args[0] + val : undefined );

  if (arguments.length >= 2 && typeof(args[1]) == 'number'){
    return args[0] + args[1];
  } else
  return undefined; 

}

//test code
addTogether("2", 3); // gives 23, not 5 as expected

Challenge:
Arguments Optional

Link to the challenge:

Thank you for helping make FCC better. Bugs can be reported as GitHub Issues. Whenever reporting a bug, please check first that there isn’t already an issue for it and provide as much detail as possible.

Like this one?

addTogether("https://www.youtube.com/watch?v=dQw4w9WgXcQ")

Oh, I think you mean where the first argument isn’t a valid number but the second is.

Oh, I think you mean where the first argument isn’t a valid number but the second is .

Exactly! I edited the sentence. I think the test case in the code was clear.
Thank you for your reply!