Is a function that calls Math.random() pure?

Question

Is the following a pure function?

function test(min,max) {
   return  Math.random() * (max - min) + min;
}

My understanding is that a pure func

Answer 1

No, it isn't. You can't figure out the result at all, so this piece of code can't be tested. To make that code testable, you need to extract the component that generates the random number:

function test(min, max, generator) {
  return  generator() * (max - min) + min;
}

Now, you can mock the generator and test your code properly:

const result = test(1, 2, () => 3);
result == 4 //always true

And in your "production" code:

const result = test(1, 2, Math.random);