title: vue.js Cannot find element #app
body: <p>learning custom plugins, I am trying to test w a virtual DOM </p>
  
  <pre><code>import Vue from 'vue'
  import MyPlugin from '@/plugins/MyPlugin'
  
  Vue.use(MyPlugin)
  
  describe('MyPlugin', () =&gt; {
    let vm
  
    beforeEach(() =&gt; {
      vm = new Vue({
        template: '&lt;div id="app" class="container" v-demo:hello.a.b="msg"&gt;&lt;/div&gt;',
        el: '#app',
        data: {
          msg: 'hello!'
        }
      }).$mount()
    })
  
    it('should run', () =&gt; {
      Vue.myMethod()
      console.log('INNER: ', vm.$el.innerHTML)
      expect(true).to.equal(true)
    })
  })
  </code></pre>
  
  <p>but I get an error :</p>
  
  <p>ERROR LOG: '[Vue warn]: Cannot find element: #app'</p>
  
  <p>isn't already defined in the template ??</p>
  
  <p>thanks for feedback</p>