Before:
  runtime ale_linters/markdown/markdownlint.vim

After:
  call ale#linter#Reset()

Execute(The Markdownlint handler should parse output correctly):
  AssertEqual
  \ [
  \   {
  \     'lnum': 1,
  \     'text': '(MD002/first-header-h1) First header should be a top level header [Expected: h1; Actual: h2]',
  \     'type': 'W'
  \   },
  \   {
  \     'lnum': 298,
  \     'text': '(MD033/no-inline-html) Inline HTML [Element: p]',
  \     'type': 'W'
  \   }
  \ ],
  \ ale#handlers#markdownlint#Handle(0, [
  \ 'README.md: 1: MD002/first-header-h1 First header should be a top level header [Expected: h1; Actual: h2]',
  \ 'README.md: 298: MD033/no-inline-html Inline HTML [Element: p]'
  \ ])