a validation

test.js

//1357 just a random number to get thing started

const sut = require('./index')(1357);

// should have 1000 elements
if (sut.size !== 1000) {
  console.log(sut.size);
  console.error('something goes wrong...');
}

// should have no duplicate numbers
[
  /11/,
  /22/,
  /33/,
  /44/,
  /55/,
  /66/,
  /77/,
  /88/,
  /99/,
  /00/
].forEach(regex => {
  sut.forEach(item => {
    if (regex.test(item)) {
      console.log(item);
      console.error('something goes wrong...');
    }
  });
});

// should have no consecutive numbers
Array.from(sut).forEach(item => {
  const numArray = item
    .toString()
    .split('')
    .map(item => parseInt(item));

  [0, 1, 2].forEach(index => {
    if (
      numArray[index] ===
      numArray[index + 1] - 1
    ) {
      console.log(item);
      console.error('something goes wrong...');
    }
  });
});