Execute (enable only scss preprocessor):
  let g:vue_pre_processors = ['typescript']

Given vue:
  <template lang="pug">
    .some-class
  </template>
  <script lang="typescript">
  @Component({})
  </script>

Execute (only scss is highlighted):
  Assert SyntaxOf('.some-class') !~# '^pug', "pug shouldn't be highlighted"
  Assert SyntaxOf('@Component({})') =~# '^typescript', "typescript should be highlighted"
  unlet g:vue_pre_processors