JavaScriptでフォームの自動入力を実現する！テスト時の面倒な入力とおさらば！

// フォーム値を取得してlocalStorage に保存
function getFormValue(storage_key, form) {
  var active_form, params, targets;
  params = {};
  active_form = $(form);
  targets = 'input[type=text], textarea, input[type=number], input[type=hidden], select';

  $(targets, active_form).each(function() {
    // key:name属性 val:フォーム値
    params[$(this).attr('name')] = $(this).val();
  });

  // 削除したい要素のkeyを記述
  delete params['utf8'];
  delete params['authenticity_token'];

  localStorage.setItem(storage_key, JSON.stringify(params));
};

// 過去の入力値を呼び出して利用
function setFormValue(storage_key){
  params = JSON.parse(localStorage.getItem(storage_key));

  for(var key in params){
    if("hidden" != $("[name='"+key+"']").attr("type")){
      $("[name='"+key+"']").val(params[key]);
    }
  }
}

  // 削除したい要素のkeyを記述
  delete params['utf8'];
  delete params['authenticity_token'];
  delete params['name属性'];

<script>
  setFormValue('formName');
</script>

getFormValue('formName', 'form');

localStorage.getItem('formName');