let testArray = [2, 3, 4];

function sumArray(sumArr) {
  let add = sum(sumArr[0],sumArr[1])[0] + sumArr[2];
  return [add,`${sumArr[0]},${sumArr[1]},${sumArr[2]} was passed in as an array of numbers, and ${add} is their sum.`]
}

testSumArray(testArray);