Before:
  call ale#assert#SetUpLinterTest('markdown', 'markdownlint')

After:
  call ale#assert#TearDownLinterTest()

Execute(The default command should be correct):
  AssertLinter 'markdownlint', ale#Escape('markdownlint') . ' %s'

Execute(The options should be configurable):
  let g:ale_markdown_markdownlint_options = '--config ~/custom/.markdownlintrc'

  AssertLinter 'markdownlint', ale#Escape('markdownlint') . ' --config ~/custom/.markdownlintrc %s'