gistfile1.txt

let isVowel = (letter) => {
  return (letter === 'a' || letter === 'e' || letter === 'i' || letter === 'o' || letter === 'u' || letter === 'A' || letter === 'E' || letter === 'I' || letter === 'O' || letter === 'U');
};

let vowelDoubler = (letters) => {
  for (let i = 0; i < letters.length; i++) {
    if (isVowel(letters[i])) {
      letters.splice(i, 0, letters[i]);
      i++;
    }
  }
  return letters;
};

class TestSuite {
  constructor () {
    this.passed = 0;
    this.failed = 0;
  }
  test (val1, val2, name) {
    if (JSON.stringify(val1) === JSON.stringify(val2)) {
      this.passed++;
    } else {
      this.failed++;
      console.error('Failed: ' + name + ', expected ' + JSON.stringify(val1) + ' to equal ' + JSON.stringify(val2));
    }
  }
  report () {
    console.log('Passed ' + this.passed + ' tests');
    console.log('Failed ' + this.failed + ' tests');
  }
  run () {
    this.test(vowelDoubler(['a', 'b', 'c', 'd', 'e']), ['a', 'a', 'b', 'c', 'd', 'e', 'e']);
    this.test(vowelDoubler(['a', 'a', 'b', 'e', 'o']), ['a', 'a', 'a', 'a', 'b', 'e', 'e', 'o', 'o']);
    this.test(vowelDoubler(['u']), ['u', 'u']);
    this.test(vowelDoubler(['b', 'y', 'w', 'l', 's']), ['b', 'y', 'w', 'l', 's']);
    this.report();
  }
}

new TestSuite().run();