Before:
  call ale#test#SetDirectory('/testplugin/test/fixers')
  Save g:ale_elixir_mix_executable
  Save g:ale_elixir_mix_format_options

  let g:ale_elixir_mix_executable = 'xxxinvalid'

After:
  call ale#test#RestoreDirectory()

Execute(The mix_format callback should return the correct default values):
  call ale#test#SetFilename('../elixir-test-files/testfile.ex')

  AssertEqual
  \ {
  \   'read_temporary_file': 1,
  \   'command': ale#Escape('xxxinvalid')
  \     . ' format  %t',
  \ },
  \ ale#fixers#mix_format#Fix(bufnr(''))

Execute(The mix_format callback should include the correct format options):
  let g:ale_elixir_mix_format_options = 'invalid_options'
  call ale#test#SetFilename('../elixir-test-files/testfile.ex')

  AssertEqual
  \ {
  \   'read_temporary_file': 1,
  \   'command': ale#Escape('xxxinvalid')
  \     . ' format invalid_options %t',
  \ },
  \ ale#fixers#mix_format#Fix(bufnr(''))