Before:
  call ale#assert#SetUpLinterTest('javascript', 'xo')
  call ale#test#SetFilename('testfile.jsx')
  unlet! b:executable

  set filetype=javascriptreact
  runtime autoload/ale/handlers/xo.vim

After:
  call ale#assert#TearDownLinterTest()

Execute(The default xo command should be correct):
  AssertLinter 'xo', ale#Escape('xo') . ' --reporter json --stdin --stdin-filename %s'

Execute(The xo executable and command should be configurable):
  let b:ale_javascript_xo_executable = 'foobar'
  let b:ale_javascript_xo_options = '--wat'

  AssertLinter 'foobar', ale#Escape('foobar')
  \ . ' --wat --reporter json --stdin --stdin-filename %s'