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

After:
  Restore

  call ale#test#RestoreDirectory()

Execute(The styler callback should include custom styler options):
  let g:ale_r_styler_options = "a_custom_option"

  AssertEqual
  \ {
  \   'command': 'Rscript --vanilla -e '
  \       . '"suppressPackageStartupMessages(library(styler));'
  \       . 'style_file(commandArgs(TRUE), style = '
  \       . 'a_custom_option)"'
  \       . ' %t',
  \   'read_temporary_file': 1,
  \ },
  \ ale#fixers#styler#Fix(bufnr(''))