How to test Vue in CDN mode?

I set up my vue & vuex project using cdn but not npm like this:

index.php:

<div id="app"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.1/vue.js"></script>

app.js:

const app = new Vue({
  el: '#app',
  components: {component1},
  template: `<component1 />`
})

components in js files:

export default{
  name: 'component1',
  template: `<p>Hello World</p>`
}

So that all my components are js files and I don't have a package.json. Now I'm trying to test my components using jest and @vue/test-utils, is there a way to setup test framework without using npm?