Component needing testing of an event

LoginForm.vue

<template>
  <div>
    <b-modal @shown="focusUsername">
      <b-form-input
        ref="username"
        v-model="username"
        :placeholder="Username"
      ></b-form-input>
    </b-modal>
  </div>
</template>

<script>
export default {
  data: () => ({
    username: '',
  }),
  methods: {
    focusUsername() {
      this.$refs.username.$el.focus()
    },
  },
}
</script>