Execute(The cspell handler should handle cspell output):
  AssertEqual
  \ [
  \   {
  \     'lnum': 721,
  \     'col': 18,
  \     'type': 'W',
  \     'text': 'Unknown word (stylelint)',
  \   },
  \ ],
  \ ale#handlers#cspell#Handle(bufnr(''),
  \   '/:721:18 - Unknown word (stylelint)'
  \)