webpagetest-visualtest-starter.js

const data = [
 ['My Title', 'https://example.org'],
 // more...
];
const min = 1;
const max = data.length;

for (let i = min; i < max; i++) {
  document.querySelector('#visual_comparison button').click();
}

for (let i = min; i <= max; i++) {
  const di = i-min;
  
  document.querySelector(`#urls #label${i}`).value = data[di][0];
  document.querySelector(`#urls #url${i}`).value = data[di][1];
}