title: Emit keydown event with key modifier on a stub in vue-test-utils
body: <p>I have a auto-stubbed child component with a keydown event with a <code>.down</code> modifier. I want to trigger this event in my test.</p>
  
  <p><strong>Somewhere in component.vue:</strong></p>
  
  <pre><code>&lt;child-component @keydown.down="myFn()" /&gt;
  </code></pre>
  
  <p><strong>Somewhere in component.spec.js:</strong></p>
  
  <pre><code> // I expect the keydown.down event to be triggered:
   wrapper.find({name: 'child-component'}).vm.$emit('keydown.down')
  </code></pre>
  
  <p>This doesn't work. The only way I was able to trigger the event is when i remove the modifier <code>.down</code>, or if I add a <code>.native</code> modifier to the event. Unfortunately I'm  unable to use the <code>.native</code> modifier.</p>
  
  <p><strong>Other things I've tried:</strong></p>
  
  <p><code>wrapper.find({name: 'child-component'}).trigger('keydown.down')</code></p>
  
  <p><code>wrapper.find({name: 'child-component'}).vm.$emit('keydown', {keyCode: 40})</code></p>