Testing randomness function without intended mean

I have a program that tests a randomness function for how truly random it is:

function testRandom(randomF, tests, intendedMean){
  
  let total = 0;
  
  for(let t = 0; t < tests; t++){
    
    total+=randomF();
    
  }
  
  return Math.abs((total/tests) - intendedMean);
  
}

const randomFunc = () => { return ~~(Math.random() * 2) + 1 }
//returns a randomly choosen 1 or 2.

console.log(testRandom(randomFunc, 100, 1.5));

But is their a way to take out the intended mean and still have a relatively accurate output? My ideas so far are to create a standard deviation set up, but I'm not sure that's the right idea.