Before:
  Save g:ale_proto_buf_format_executable

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

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

After:
  Restore

  call ale#test#RestoreDirectory()

Execute(The buf-format callback should return the correct default values):
  call ale#test#SetFilename('../test-files/proto/testfile.proto')

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