message: question.cssClasses, vue implementation
  --  removed question css from test
diff: @@ -49,7 +49,6 @@ QUnit.test("Survey.Checkbox initialization and values", (assert) => {
  const vm = new Checkbox;
  vm.question = question;
  - vm.css = survey.css;
  vm.$mount();
  assert.deepEqual(question.value, ["second item"]);
  @@ -67,7 +66,6 @@ QUnit.test("Survey.Checkbox question changed", (assert) => {
  const vm = new Checkbox;
  vm.question = question1;
  - vm.css = survey.css;
  vm.$mount();
  assert.deepEqual(vm.value, ["second item"]);
  @@ -82,7 +80,6 @@ QUnit.test("Survey.Checkbox question value in model has been changed", function
  const vm = new Checkbox;
  vm.question = question;
  - vm.css = survey.css;
  vm.$mount();
  assert.deepEqual(vm.value, ["second item"]);
  