docs: function (value1, value2, tolerance, optMsg) {
                  var msg;
  
                  if (optMsg) {
                      msg = ariaUtilsString.substitute(optMsg, ['"' + value1 + '"', '"' + value2 + '"']);
                  } else {
                      msg = 'First value: ' + value1 + ', second value: ' + value2 + ', tolerance was: ' + tolerance;
                  }
  
                  this.assertTrue((Math.abs(value1 - value2) <= tolerance), msg);
              }