Before:
  Save g:ale_sh_shfmt_executable
  Save g:ale_sh_shfmt_options

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

Execute(The shfmt callback should return the correct default values):
  AssertEqual
  \ {
  \   'command': ale#Escape('xxxinvalid'),
  \ },
  \ ale#fixers#shfmt#Fix(bufnr(''))

Execute(The shfmt callback should include custom shfmt options):
  let g:ale_sh_shfmt_options = '--some-option'

  AssertEqual
  \ {
  \   'command': ale#Escape(g:ale_sh_shfmt_executable)
  \     . ' --some-option',
  \ },
  \ ale#fixers#shfmt#Fix(bufnr(''))