title: Testing v-slots with v-for - Jest / Vue
body: <p>I am trying to figure out how to test my component which has v-slot in it. 
  Structure of component template:</p>
  
  <p><strong>Grid.vue</strong></p>
  
  <pre><code>&lt;div&gt; 
     &lt;v-slot&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>And when I call it it is something like:</p>
  
  <pre><code>&lt;Grid&gt;
     &lt;Column v-for="(element, index) in list" :key=index /&gt; 
  &lt;/Grid&gt;
  </code></pre>
  
  <p>So far I've got that :</p>
  
  <pre><code>import { mount } from '@vue/test-utils';
  import Grid from '~/components/Grid';
  import GridColumn from '~/components/Column';
  
  const columns = [
      {
          id: 'col1',
      },
      {
          id: 'col2',
      },
  ];
  
  describe('Grid.vue', () =&gt; {
      const columnWrapper = {
          // render(h) {
          //     return columns.map(function (item) {
          //         return h('Column', item.id) })
          // }
          render(h) {
              return h(Column, { props: { index: 1, column: columns[0] } });
          }
      };
  
      const wrapper = mount(Grid, {
          slots: { columnWrapper }
      });
  });
  </code></pre>
  
  <p>I did write 2 ways of rendering slots for <code>Grid</code>. The second one with <code>return h(Column....</code> is creating only one column. How could I render columns = number of columns model list ? The first option / commented I am not sure If I have written it well - <code>return h('Column' ....</code> - that might be wrong.</p>
  
  <p>When I console log <code>wrapper.vm.$el.children</code> the <code>HTMLCollection</code> is empty. Columns weren't added into <code>Grid</code>. Does any one know what am I doing wrong ?</p>