title: el-checkbox cannot be set checked with jest or at least no change on v-model
body: <p>I'm setting up some tests for my vuejs website. I'm using <a href="https://element.eleme.io/" rel="nofollow noreferrer">element-ui</a>. I'm trying jest on my connection page. I have a checkbox linked to a "remember me". I'd to check it and check if the value of the v-model changed.</p>
  
  <p>Unfortunately, it doesn't.</p>
  
  <p>In my connection file, I've the checkbox :</p>
  
  <pre><code>...
    &lt;el-checkbox v-model="connectionForm.rememberme"&gt;&lt;/el-checkbox&gt;
  ...
  </code></pre>
  
  <p>And the rememberme variable :</p>
  
  <pre><code>...
    data() {
      return {
        connectionForm: {
          ...
          rememberme: false
        },
  ...
  </code></pre>
  
  <p>My test file :</p>
  
  <pre><code>
  describe('Connection', () =&gt; {
    const wrapper = mount(Connection)
  
    it('checkbox click', () =&gt; {
      expect(wrapper.vm.connectionForm.rememberme).toBe(false)
  
      expect(wrapper.contains('el-checkbox')).toBe(true)
      const elCheckbox = wrapper.find('el-checkbox')
  
      elCheckbox.setChecked(true)
      expect(wrapper.vm.connectionForm.rememberme).toBe(true)
    })
  })
  
  </code></pre>
  
  <pre class="lang-sh prettyprint-override"><code> FAIL  frontend/components/user/sessions/New.test.js
    Connexion
      ✓ has a el-button (4ms)
      ✕ checkbox click (10ms)
  
    ● Connexion › checkbox click
  
      [vue-test-utils]: wrapper.setChecked() cannot be called on this element
  
        26 | 
      &gt; 27 |     elCheckbox.setChecked(true)
           |                ^
        28 |     expect(wrapper.vm.connexionForm.rememberme).toBe(true)
        29 |   })
        30 | })
  
  </code></pre>
  
  <p><a href="https://element.eleme.io/#/en-US/component/checkbox#checkbox-group-events" rel="nofollow noreferrer">doc checkbox</a></p>
  
  <p>So, I changed the setChecked(true) with a .trigger('click'), still nothing. So, I changed 'click' to 'change', but still not working...</p>
  
  <pre class="lang-sh prettyprint-override"><code> FAIL  frontend/components/user/sessions/New.test.js
    Connexion
      ✓ has a el-button (4ms)
      ✕ checkbox click (10ms)
    ● Connexion › checkbox click
  
      expect(received).toBe(expected) // Object.is equality
  
      Expected: true
      Received: false
  
        27 |     elCheckbox.trigger('change')
      &gt; 28 |     expect(wrapper.vm.connectionForm.rememberme).toBe(true)
           |                                                  ^
        29 |   })
        30 | })
        31 | 
  
  </code></pre>
  
  <p>If found somewhere this :</p>
  
  <pre><code>    elCheckbox.element.selected = true
  </code></pre>
  
  <p>But changes nothing.</p>