title: What are "stubbed child components" in Vue Test Utils?
body: <p><a href="https://vue-test-utils.vuejs.org" rel="noreferrer">Vue Test Utils</a> has an API method called <a href="https://vue-test-utils.vuejs.org/api/#shallowmount" rel="noreferrer"><code>shallowMount()</code></a> that:</p>
  
  <blockquote>
    <p>...creates a <code>Wrapper</code> that contains the mounted and rendered Vue component, but with stubbed child components.</p>
  </blockquote>
  
  <p>I've searched the Vue Test Utils documentation website but failed to find a good explanation of how these stubbed child components behave.</p>
  
  <ol>
  <li>What exactly are these stubbed child components? </li>
  <li>Which parts of the Vue component lifecycle do they go through? </li>
  <li>Is there a way to pre-program their behavior?</li>
  </ol>