Before:
  runtime ale_linters/markdown/mdl.vim

After:
  call ale#linter#Reset()

Execute(The mdl handler should parse output correctly):
  AssertEqual
  \ [
  \   {
  \     'lnum': 1,
  \     'code': 'MD002/first-header-h1',
  \     'text': 'First header should be a top level header',
  \     'type': 'W'
  \   },
  \   {
  \     'lnum': 18,
  \     'code': 'MD033/no-inline-html',
  \     'text': 'Inline HTML',
  \     'type': 'W'
  \   }
  \ ],
  \ ale_linters#markdown#mdl#Handle(0, [
  \     '[{"filename":"README.md","line":1,"rule":"MD002","aliases":["first-header-h1"],"description":"First header should be a top level header"},{"filename":"README.md","line":18,"rule":"MD033","aliases":["no-inline-html"],"description":"Inline HTML"}]'
  \ ])