title: Getting [Vue warn]: Unknown custom element: <b-modal> even though bootstrap-vue is registered
body: <p>A BootstrapVue b-modal component in a custom Vue component loads correctly in the browser. However, when testing using mocha+mochapack, it generates a Vue warning that the b-modal element is not registered. The test is using a localVue object that has BootstrapVue registered. All other bootstrap custom elements seem to be loading correctly, and do not generate any warnings.</p>
  
  <p>I tried various things, including importing BModal from 'bootstrap-vue' and registering it as a component directly, but still got the same error.</p>
  
  <pre><code>import {mount, createLocalVue} from "@vue/test-utils"
  import MyCustomModal from '../js/MyCustomModal';
  
  const localVue = createLocalVue();
  
  import BootstrapVue from 'bootstrap-vue'
  localVue.use(BootstrapVue);
  
  describe('MyCustomModal', () =&gt; {
      let wrapper = mount(MyCustomModal,{
              localVue
          });
  
      it('the content is "this is the content"', () =&gt; {
          expect(wrapper.find(".modal-content").text()).toEqual('this is the content');
      });
  
  
  });
  
  </code></pre>
  
  <p>The custom Vue component:</p>
  
  <pre><code>&lt;template&gt;
      &lt;b-modal&gt;
          &lt;div class="modal-content"&gt;this is the content&lt;/div&gt;
          &lt;b-form&gt;
             my form
          &lt;/b-form&gt;
      &lt;/b-modal&gt;
  &lt;/template&gt;
  
  &lt;script&gt;
      export default {
          data(){
              return {};
          }
      }
  &lt;/script&gt;
  </code></pre>
  
  <p>The tests run correctly and pass, but it outputs the Vue warning for the b-modal element. It doesn't output the warning for b-form.</p>