Before:
  call ale#assert#SetUpFixerTest('html', 'html-beautify', 'beautify')

  call ale#test#SetDirectory('/testplugin/test/fixers')
  silent cd ..
  silent cd command_callback

After:
  Restore

  call ale#assert#TearDownFixerTest()

Execute(The html-beautify callback should return the correct default command):
  AssertEqual
  \ {'command': '''html-beautify''  -'},
  \ ale#fixers#html_beautify#Fix(bufnr(''))