Change the way the test references the textarea

app/assets/javascripts/notes/components/discussion_reply_placeholder.vue

@@ -12,6 +12,7 @@ export default {
 
 <template>
   <textarea
+    ref="textarea"
     rows="1"
     class="reply-placeholder-text-field js-vue-discussion-reply"
     :placeholder="placeholderText"

spec/frontend/notes/components/discussion_reply_placeholder_spec.js

@@ -6,7 +6,7 @@ const placeholderText = 'Test Button Text';
 describe('ReplyPlaceholder', () => {
   let wrapper;
 
-  const findTextarea = () => wrapper.find('.js-vue-discussion-reply');
+  const findTextarea = () => wrapper.find({ ref: 'textarea' });
 
   beforeEach(() => {
     wrapper = shallowMount(ReplyPlaceholder, {