function allChars(start = undefined, end = undefined) {
  start = start || 0;
  end = end || 256;
  let rv = '';
  for (let i = start; i < end; i++) {
    rv += String.fromCharCode(i);
  }
  return rv;
}
Test cases for googString.floatAwareCompare and googString.intAwareCompare.
Each comparison in this list is tested to assure that terms[0] < terms[1],
terms[1] > terms[0], and identity tests terms[0] == terms[0] and
terms[1] == terms[1].
@const {!Array<!Array<string>>}