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

After:
  call ale#assert#TearDownLinterTest()

Execute(The default command should be correct):
  AssertLinter 'harper-ls', ale#Escape('harper-ls') . ' --stdio'

Execute(Should accept configuration settings):
  AssertLSPConfig g:ale_markdown_harper_config

  let b:ale_markdown_harper_config = {'harper-ls': {'diagnosticSeverity': 'warning'}}
  AssertLSPConfig {'harper-ls': {'diagnosticSeverity': 'warning'}}