Before:
  Save g:ale_haskell_hfmt_executable

  " Use an invalid global executable, so we don't match it.
  let g:ale_haskell_hfmt_executable = 'xxxinvalid'

  call ale#test#SetDirectory('/testplugin/test/fixers')

After:
  Restore

  call ale#test#RestoreDirectory()

Execute(The hfmt callback should return the correct default values):
  call ale#test#SetFilename('../haskell_files/testfile.hs')

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