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

After:
  call ale#assert#TearDownLinterTest()

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

Execute(The executable should be configurable):
  let g:ale_markdown_markdownlint_executable = 'foo bar'
  let g:ale_markdown_markdownlint_options = '--option'

  AssertLinter 'foo bar', ale#Escape('foo bar') . ' --option %s'