vue/test/unit/features/options/comments.spec.ts

import Vue from 'vue'

describe('Comments', () => {
  it('comments should be kept', () => {
    const vm = new Vue({
      comments: true,
      data() {
        return {
          foo: 1
        }
      },
      template:
        '<div><span>node1</span><!--comment1-->{{foo}}<!--comment2--></div>'
    }).$mount()
    expect(vm.$el.innerHTML).toEqual(
      '<span>node1</span><!--comment1-->1<!--comment2-->'
    )
  })
})