title: Vue test utils: '[object Object]' is not a valid selector
body: <p>I'm trying to get an element by its <code>ref</code> attribute from the wrapper, but it is throwing an error shown below.</p>
  <p>According to the <a href="https://vue-test-utils.vuejs.org/api/selectors.html#find-option-object" rel="nofollow noreferrer">documentation</a>, my usage of <code>find</code> seems to be correct.</p>
  <pre><code> SyntaxError: '[object Object]' is not a valid selector
  
    13 |     const lis = wrapper.findAll('li');
    14 | 
  &gt; 15 |     const a = wrapper.find({ ref: 'first' });
       |                       ^
    16 | 
    17 |     console.log(a);
    18 | 
  
    at emit (node_modules/nwsapi/src/nwsapi.js:565:17)
    at _querySelectorAll (node_modules/nwsapi/src/nwsapi.js:1513:9)
    at Object._querySelector [as first] (node_modules/nwsapi/src/nwsapi.js:1424:14)      at VueWrapper.find (node_modules/@vue/test-utils/dist/vue-test-utils.cjs.js:192      at Object.it (tests/unit/example.spec.js:15:23)
  </code></pre>